The Norwegian Nobel Committee countered that it was trying "to promote what he stands for and the positive processes that have started now." It 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.
"He got the prize because he has been able to change the international climate," Nobel Committee chairman Thorbjoern Jagland said. "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. It is now that we have the opportunity to respond – all of us."
Archbishop Desmond Tutu of South Africa, who won the prize in 1984, said Obama's award shows great things are expected from him in coming years.
"It's an award coming near the beginning of the first term of office of a relatively young president that anticipates an even greater contribution towards making our world a safer place for all," Tutu said. "It is an award that speaks to the promise of President Obama's message of hope."
Obama is the third sitting U.S. president to win the award: President Theodore Roosevelt won in 1906 and President Woodrow Wilson was awarded the prize in 1919.
Wilson received the prize for his role in founding the League of Nations, the hopeful but ultimately failed precursor to the contemporary United Nations.
The Nobel committee chairman said after awarding the 2002 prize to former Democratic President Jimmy Carter, for his mediation in international conflicts, that it should be seen as a "kick in the leg" to the Bush administration's hard line in the buildup to the Iraq war.
In a major surprise, even to the White House, President Barack Obama was awarded the Nobel Peace Prize today, making him the third sitting U.S. president to win the prestigious award.
White House Press Secretary Robert Gibbs, who woke the president to tell him the news, said Obama was humbled.
The nomination deadline was just 11 days into Obama's presidency.
Geir Lundestad, director of the Norwegian Nobel Institute, told "Good Morning America" the decision was unanimous.
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