Nobel officials said their stunning pick was meant to build momentum behind Obama's initiatives to reduce nuclear arms, ease tensions with the Muslim world and stress diplomacy and cooperation rather than unilateralism.
The president will donate the entire $1.4 million prize to charity, White House spokesman Robert Gibbs said, but hasn't decided yet which organizations will share the windfall.
"I do not feel that I deserve to be in the company of so many transformative figures that have been honored by this prize," he said. "I will accept this award as a call to action, a call for all nations to confront the challenges of the 21st century."
Many observers were shocked by the unexpected choice so early in the Obama presidency, which began less than two weeks before the Feb. 1 nomination deadline and has yet to yield concrete achievements in peacemaking.
Some around the world objected to the choice of Obama, who still oversees wars in Iraq and Afghanistan and has launched deadly counter-terror strikes in Pakistan and Somalia.
Obama said he was working to end the war in Iraq and "to confront a ruthless adversary that directly threatens the American people and our allies" in Afghanistan.
Vote of confidenceMembers of the Norwegian Nobel Committee said their choice could be seen as an early vote of confidence in Obama intended to build global support for his policies. They lauded the change in global mood wrought by Obama's calls for peace and cooperation, and praised his pledges to reduce the world stock of nuclear arms, ease American conflicts with Muslim nations and strengthen the U.S. role in combating climate change.
Aagot Valle, a lawmaker for the Socialist Left party who joined the committee this year, said she hoped the selection would be viewed as "support and a commitment for Obama."
"And I hope it will be an inspiration for all those that work with nuclear disarmament and disarmament," she told The Associated Press in a rare interview. Members of the Nobel peace committee usually speak only through its chairman.
The peace prize was created partly to encourage ongoing peace efforts but Obama's efforts are at far earlier stages than past winners'. The Nobel committee acknowledged that they may not bear fruit at all.
"Some people say, and I understand it, isn't it premature? Too early? Well, I'd say then that it could be too late to respond three years from now," Nobel Committee chairman Thorbjoern Jagland said. "It is now that we have the opportunity to respond — all of us."
Star power?In Europe and much of the world Obama is lionized for bringing the United States closer to mainstream global thinking on issues like climate change and multilateralism. A 25-nation poll of 27,000 people released in July by the Pew Global Attitudes Project found double-digit boosts to the percentage of people viewing the U.S. favorably in countries around the world. That indicator had plunged across the world under President George W. Bush.
At home, the picture is more complicated. Obama is often criticized as he attempts to carry out his agenda — drawing fire over a host of issues from government spending to health care to the conduct of the war in Afghanistan.
U.S. Republican Party Chairman Michael Steele contended that Obama won the prize as a result of his "star power" rather than meaningful accomplishments.
"The real question Americans are asking is, 'What has President Obama actually accomplished?'" Steele said.
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Vote: Is Obama deserving of the prize?
Drawing criticism from some on the left, Obama has been slow to bring troops home from Iraq and the real end of the U.S. military presence there won't come until at least 2012.
In Afghanistan, he is seriously considering ramping up the number of U.S. troops on the ground and asking for help from others, too.
"I don't think Obama deserves this. I don't know who's making all these decisions. The prize should go to someone who has done something for peace and humanity," said Ahmad Shabir, 18-year-old student in Kabul. "Since he is the president, I don't see any change in U.S. strategy in the wars in Iraq and Afghanistan."
Too early?Obama has said that battling climate change is a priority. But the U.S. seems likely to head into crucial international negotiations set for Copenhagen in December with Obama-backed legislation still stalled in Congress.
Former Polish President Lech Walesa, who won the prize in 1983, questioned whether Obama deserved it now.
"So soon? Too early. He has no contribution so far. He is still at an early stage. He is only beginning to act," Walesa said. related sites www.study-us.info