Obama also urged Karzai to implement electoral reforms to cut down in the 2014 presidential election the kind of corruption that tarnished Karzai's re-election in 2009.

The pair were speaking at the opening of a two-day NATO summit in Chicago aimed at drawing up detailed plans for the withdrawal of the U.S.-led, 130,000-strong international force by the end of 2014, and for a more modest presence beyond that date.

After their meeting, Karzai reaffirmed his support for a timetable, which requires the Afghan army to take over the lead in combat by the middle of next year.

President Karzai added that he was "very much looking forward to an end to the war" and the day when Afghanistan would "no longer be a burden on the world".

President Obama said the NATO summit was about "painting a vision, post-2014, in which we have ended our combat role, the Afghan war as we understand it is over, but our commitment to friendship and partnership with Afghanistan continues."

He added: "Both of us recognize that we still have a lot of work to do. The loss of life continues in Afghanistan. There will be hard days ahead, but we're confident that we're on the right track."

Upon arrival near the convention center where the summit is taking place, one veteran threw his medals on the road, calling them symbols of lies. "I choose human life over war," Jerry Bordeleau shouted through a microphone.

Dozens of veterans followed suit, with many dedicating their medals to the children of Afghanistan and Iraq.

"This isn't an easy decision for anybody here,” Steven Acheson, an Army veteran, said before sending off his medals. He served for five years, including more than a year in Iraq.

"Hold this in your heart," Aaron Hughes, a 30-year-old organizer for Iraq Veterans Against the War, who served six years in the Army, including 15 months in Iraq and Kuwait, said after tossing two service medals. "We’ve lost too much."

With the veterans were a dozen Afghans who waved the Afghan flag and held up two fingers making peace signs.

Supporters of Chen Guangcheng have warned that his family and friends in China are still at risk after the blind activist arrived in New York to begin a new life in the United States.

Chen - whose daring escape from house arrest last month prompted a diplomatic crisis - arrived on Saturday night to cheering crowds, and used his first speech to press for greater rule of law in the country he left behind.

"I hope everybody works for me to promote justice and fairness in China," Chen said through an interpreter, ahead of his enrollment for a fellowship in the U.S.-Asia Law Institute at New York University School of Law.

He was also careful to thank the Chinese government, knowing the well-being of relatives and associates could be influenced by an upcoming shift in the Communist party leadership. Instead, he criticized the provincial authorities in Shandong for years of persecution, including 18 months of house arrest, beatings and harassment of his relatives.

Chen said "acts of retribution may not have abated" in his village of Dongshigu, which was still under lock-down. "We hope to see a thorough investigation into these events," he said.

Abdelbaset's brother, Abdelnasser al-Megrahi, confirmed reports that he had died aged 60 after a long battle with cancer. Abdelnasser, who was at the house in Tripoli where his dead brother lay on Sunday, told the Guardian: "I don't want to talk right now, I am very upset, I don't really feel like talking. He's dead, that's it, what more do you have to know?"

In an interview with the Guardian earlier this year, Abdelnasser said that his brother, who had moved to the secret address from his large home in Tripoli, was innocent. "He really is ill, he is too ill to even change the channel on the TV, he is lying down all day."

The Scottish government and East Renfrewshire Council are investigating the claims of Megrahi's death. The Foreign Office is awaiting their confirmation. Megrahi was the only man convicted of the bombing, which killed 270 people, including 11 on the ground, when Pan Am Flight 103 blew up over Lockerbie four days before Christmas in 1988.

There was no immediate reaction from the Libyan government.

Confronting an economic crisis that threatens them all, U.S. President Barack Obama and leaders of other world powers on Saturday declared that their governments must both spark growth and cut the debt that has crippled the European continent and put investors worldwide on edge.

“There's now an emerging consensus that more must be done to promote growth and job creation right now,” President Obama proclaimed after hosting unprecedented economic talks at Camp David, Maryland, his secluded and highly secure mountaintop retreat. Seeking a second term amid hard economic times, President Obama hailed a debate heading in the direction he likes, with nations now talking of ways to spark their economies instead of just slashing spending.

Yet there were no bold prescriptions at hand. Instead, leaders seemed intent on trying to inspire confidence by agreeing on a broad strategy no matter their differences. With all of them facing their own difficult political realities, they built some sovereign wiggle room into their pledge to take all necessary steps, saying “the right measures are not the same for each of us.”

President Obama played international host as Europe's debt crisis threatens to drag down the U.S. recovery and his own political future, underscoring the stakes for him in getting allies abroad to rally around some answers.

Much of the new emphasis on government-led growth seemed aimed at German Chancellor Angela Merkel, who came to the summit as the European leader who had demanded austerity as the most important step toward easing the euro-zone's debt crisis. The election of Socialist François Hollande as President of France, and Greek elections that created political chaos in the country were clear rejections of the belt-tightening Merkel represented.

Their host in Fort McMurray was Gitzikomin Deranger, Gitz to his friends – a 6-foot-4 Dene-Blackfoot activist who lives in a comfortably cluttered duplex with his parents and a revolving assortment of relatives. Many of them crowded in to meet the Achuar, who relaxed on Deranger's leather couch with surprising ease for people who live in palm huts. He had welcomed them to Alberta with a smudge – having set a small pile of sage to smoulder in a miniature cast-iron pan, he fanned smoke over his guests with an eagle feather.

“Did you kill the bird to get it?” asked Peas Peas Ayui (PAY-us PAY-us AY-wee), the group's leader, a taciturn man in his mid-40s with gold-capped upper teeth.

“No,” said Deranger, “we only use feathers that are given. If you find a feather on the ground, it means the eagle put it there for you, maybe even gave up its life for you.” The Achuar talked this over briefly and, for the first time since landing, their lips curled into smiles.

“Condor feathers are sacred for us too, but we never pick them off the ground,” Mr. Ayui explained. “To do so is an omen that your wife is preparing to leave you.” The group's female representative, a butterfly of a woman named Puwanch Kintui Antich, giggled her affirmation.

That was the first of many same-but-differents that the South and North American Natives would discover about each other through the weekend. But few of the lessons to follow would end in laughter.

Over the course of three days spent visiting reserves, band offices and the vast sand dunes left behind by the bitumen-scrubbers surrounding Fort McMurray, the Achuar confronted a reality that may one day be their own. And they didn't much like what they saw.

This encounter was born of a new dynamic: the age of extreme oil. Gone are the days of sweet Texas crude and boundless Arabian oil fields, when petroleum lay so near the surface that all a company had to do was prick the Earth's crust and let the black gold gush. To the environmentalists who worry about reaching “peak oil” (and a subsequent decline in fossil fuels), critics can point out accurately enough that the world is flush with new hydrocarbon reserves. They are less quick to acknowledge the epic complexity and risks of most of these new finds.

Alberta's oil sands are the obvious example: Here, on average, two tonnes of earth must be strip-mined and seven barrels of water heated to steam in order to produce a barrel of oil. It takes a barrel's worth of energy to produce just three barrels of oil; 30 years ago it would have been 100.

One of the most influential figures in modern psychiatry has apologized to America's gays for a scientific study which supported attempts to "cure" people of their homosexuality.

The survey, published in 2001, looked at "reparative therapy" and was hailed by religious and social conservatives in America as proof that gay people could successfully become straight if they were motivated to do so.

Dr. Robert Spitzer has now apologized in the same academic journal that published his original study, calling it "fatally flawed". "I believe I owe the gay community an apology," his letter said. "I also apologize to any gay person who wasted time and energy undergoing some form of reparative therapy because they believed that I had proven that reparative therapy works."

Spitzer's letter, which was leaked online before its publication in the Archives of Sexual Behavior, is sure to cause delight among gay civil rights groups and stir up anger among social conservatives, who have used the study to combat the acceptance of homosexuality as a normal part of human society.

Reparative therapy is popular among Christian conservative groups, which run clinics and therapy sessions at which people try to become heterosexual through counseling. Gay rights activists condemn such practices as motivated by religious faith, not science, and call them "pray away the gay" groups.

A plan to restore order in Montreal, Quebec, Canada, appeared to erupt in smoke late Saturday, with a fiery blockades blazing on busy downtown streets.

Groups of protesters built pyres from plastic traffic cones, setting them ablaze, and in at least one case added a barricade made of construction materials.

Police charged protesters and repeatedly warned that they would be incarcerated throughout the weekend unless they dispersed.

Late Saturday night they had reported more than 30 arrests.

Some bystanders accused the police of using excessive force on a crowd whose members were mostly peaceful.

Meanwhile, the protest has spread beyond borders.

In New York, members of the Montreal-based rock band “Arcade Fire” wore the movement’s iconic red squares during an appearance on Saturday Night Live. A day earlier, players in Quebec’s film industry were sporting them at the Cannes Film Festival.

The scenes unfolded on Quebec’s first full day under emergency legislation designed to end months of unrest.

Twenty-two states and the District of Columbia are backing the state of Montana in its fight to prevent the U.S. Supreme Court's 2010 Citizens United decision from being used to strike down laws restricting corporate spending in political campaigns.

The states, led by New York, are asking the high court to preserve Montana's state-level regulations on corporate expenditures, according to a copy of a brief written by New York's Attorney General's office and obtained by the Associated Press. The brief will be publicly released on Monday.

The Supreme Court is being asked to reverse a state court's decision to uphold the Montana law. Virginia-based American Tradition Partnership is asking the nation's high court to rule without a hearing because the group says the state law conflicts directly with the Citizens United decision that removed the federal ban on corporate campaign spending.

The Supreme Court has blocked the Montana law until it can look at the case.

The Montana case has prompted critics to hope the court will reverse itself on the controversial Citizens United ruling. The 22 states and District of Columbia say the Montana law is sharply different from the federal issues in the Citizens United case, so the ruling shouldn't apply to Montana's or other state laws regulating corporate campaign spending.

The states also said they would support a Supreme Court decision to reconsider portions of the Citizens United ruling either in a future case or in the Montana case, if the justices decide to take it on.

A second Greek vote next month backing parties opposed to the European Union's bailout package would be a decisive vote to leave the euro for which contingency plans have to be made now, British Prime Minister David Cameron warned on Sunday in a dramatic raising of the stakes.

Speaking in Chicago after two days of talks with world leaders on the euro crisis, he said: "We now have to send a very clear message to people in Greece: there is a choice – you can either vote to stay in the euro, with all the commitments you've made, or if you vote another way you're effectively voting to leave."

His remarks are, in effect, an attempt to make next month's vote a referendum on continued membership of the euro.

Cameron indicated that he wanted to make the threat of ejection from the euro credible by showing the Greeks that preparations are being made for their departure, a change of tactics after weeks of mixed messages from the European commission on whether such plans are being laid.

It is a piece of high-stakes diplomacy since his threat may either anger Greek voters, driving them into the arms of the radical parties, or act as a sobering warning that the end game is truly imminent and renegotiation of the E.U.-imposed austerity package is not an option.

The Center for Free Elections and Democracy, an independent polling group, said Nikolic won 49.4 percent of the vote, while pro-European Union incumbent Boris Tadic received 47.4 percent. Tadic conceded defeat, saying, "I wish Nikolic the best of luck." The results are expected to be officially confirmed by Monday.

The outcome was a sign of the fading allure of the E.U., which is plagued by a debt crisis, and voter discontent with Serbia's weak economy.

Nikolic must name a prime minister, but that task has been complicated because of the outcome of the May 6 parliamentary election. Although Nikolic's Progressive Party won the most seats, Tadic's Democrats have tentatively agreed on an alliance with Socialists that would give them a majority. Nikolic has claimed the May 6 vote was marred by fraud.

"We'll see what will happen," said Nikolic as his supporters chanted his nickname, "Tomo the Serb," on the main squares in Serbian cities.

Three thousand people in northern Italy bedded down in tents or temporary accommodation on Sunday night after a strong earthquake in the early hours killed five people, injured scores more and toppled centuries-old churches and clock towers.

Aftershocks in the Emilia-Romagna region continued to bring down damaged buildings during the day, injuring a firefighter, as emergency services scrambled to find temporary shelter for residents afraid to return home.

"Right now our absolute priority is for people to spend the night in acceptable conditions," said civil protection chief Franco Gabrielli. With storms forecast for the area, the Italian government was due to meet on Tuesday to consider declaring a state of emergency.

The 6.0 magnitude earthquake, which struck the Emilia-Romagna region 3.2 miles below ground at 4:04 a.m., was felt across northern Italy, from Liguria to the Veneto, and was described by one official as the worst in the area since the 1300s. The last serious earthquake to strike Italy was the 6.3 magnitude shock in L'Aquila in 2009 that killed nearly 300.

"There's nothing to be done," said Valeria Balboni, standing amid shattered glass in her family's bathroom fittings factory near Sant'Agostino. "We're going to have to close, like so many of the others."

The earthquake left major towns such as Bologna unscathed but wrought havoc in small towns and villages dotting the countryside between Bologna, Ferrara and Modena.

Economic stimulus is making a comeback.

The most notable thing about the Group of Eight Summit in Maryland on Friday and Saturday was the recognition that austerity isn’t a universal cure for what ails the global economy, especially Europe.

U.S. President Barack Obama and France’s newly elected Socialist President, François Hollande, were the rhetorical winners on the weekend.

They successfully watered down the German-led position that the best way to deal with a debt crisis is to quickly pay down debt by shifting the consensus to an acceptance that austerity is a means, not an end. Fiscal consolidation remains a priority, but not at the expense of economic growth, a new emphasis that could reshape governments’ approach to maintaining the recovery from the financial crisis.

“The global economic recovery shows signs of promise, but significant headwinds persist,” the G-8 said in a statement. “We commit to take all necessary steps to strengthen and reinvigorate our economies and combat financial stresses, recognizing that the right measures are not the same for each of us.”

The shift reflects the acute state of the European debt crisis, which President Obama characterized on Saturday as a “serious” situation that could upend the global economic recovery. The G-8 also said it stood ready to release strategic oil reserves if crude prices surge this summer, but it was the prospect of Europe sinking into a deeper downturn that most worried leaders.

British Prime Minister David Cameron told reporters that he detected a “growing sense of urgency that action needed to be taken” on the euro-zone crisis, Reuters reported. “Contingency plans need to be put in place and the strengthening of banks, governance, firewalls – all of those things need to take place very fast,” said Cameron.

The German leader resisted pressure for fresh measures that would include looser monetary policy for the European Central Bank, enabling quantitative easing similar to that deployed by the Federal Reserve and the Bank of England.

President Obama and Prime Minister Cameron discussed their joint position at a G8 summit in Camp David during a 7 a.m. meeting held on a treadmill, possibly the first U.K.-U.S. bilateral to be conducted in a gym.

With pressure growing for world leaders to come up with a decisive plan for solving the crisis, it emerged the Germans were resisting the inclusion of details in the final communiqué about the best course of action for the euro zone.

The so-called sherpas, appointed by national leaders to draft summit communiqués, were at work until 4 a.m. on Saturday trying to forge a common position that said something specific about the euro crisis. It was being suggested that the Germans, partly due to their isolation at the summit, were pressing for specifics to be deferred to an informal E.U. council later this week, arguing it was not the business of the G-8, including Canada, Russia, Japan and the U.S., to tell the E.U. states how to handle their economy. Cameron's aides took the view that it would look distinctly odd if the communiqué did not highlight solutions.

A strong earthquake rocked a large swathe of northern Italy early on Sunday morning, causing at least three deaths and collapsing rural factories and ancient bell towers in towns.

The epicenter of the quake, which struck at 4:04 a.m. local time and had a magnitude of 5.9, was in the plains near Modena; but it was felt in nearby regions.

One person working a night shift died in the collapse of a factory and two others were killed in the collapse of another building. Rescue officials were checking reports that other people were buried under rubble.

First television pictures taken after dawn showed serious damage to historic buildings and rural structures. Parts of a historic fortress in one town collapsed.

Thousands of people in the area rushed into the streets after the quake, felt in the major towns of Bologna, Modena, Ferrara, Rovigo, Verona and Mantua.

A series of strong aftershocks hit the area and local mayors ordered residents to stay out of their homes.