WASHINGTON – President Barack Obama said Friday he was honored and humbled to win the Nobel Peace Prize and would accept it as a "call to action" to work with other nations to solve the problems of the 21st century.

A beaming Obama told reporters in the White House Rose Garden that he wasn't sure he had done enough to earn the award, or deserved to be in the company of the others who had won it before him.

But, 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."

Obama will travel to Oslo, Norway, in December to accept the award.

Obama, 48, is the third U.S. president to win the prize while in office, after Theodore Roosevelt and Woodrow Wilson.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

Some U.S. reaction to President Barack Obama's win of the 2009 Nobel Peace Prize on Friday:

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"I congratulate President Obama on being awarded the Nobel Peace Prize today. It is a bold statement of international support for his vision and commitment to peace and harmony in international relations. It shows the hope his administration represents not only to our nation but to people around the world." — Former President Jimmy Carter.

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"I think it's extremely well deserved. ... I think it will take some time before people put together all the different moves that linked his speech at the UN on the abolishing of nuclear weapons, his shift on the missile defense program in Eastern Europe and the movement of Russia to joining the international consensus that confronted Iran to abide by the nonproliferation treaty." — Former Vice President Al Gore.

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"The real question Americans are asking is, 'What has President Obama actually accomplished?' It is unfortunate that the president's star power has outshined tireless advocates who have made real achievements working towards peace and human rights." — Republican National Committee Chairman Michael Steele.

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"Under any circumstance an appropriate response is to say congratulations." — Gov. Tim Pawlenty, R-Minn.

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"It validates the president's approach to tough transnational challenges such as global warming and the spread of nuclear arms. And it celebrates his steady efforts to improve America's standing around the world." — Rep. Howard Berman, D-Calif., chairman of the House Foreign Affairs Committee.

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"The Nobel Committee's decision to award this year's Peace Prize to President Obama is an affirmation of the fact that the United States has returned to its long-standing role as a world leader." — Gov. Tim Kaine, D-Va., the Democratic National Committee chairman.

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"Climate change is perhaps the best example of what the Nobel Committee described as President Obama's recognition of 'global responsibility for global challenges.' ... It is clear that President Obama's elevation of the environment to the highest levels of diplomacy has helped to solidify a shared understanding that no nation can escape the impact of climate change." — Sen. Ben Cardin, D-Md.

from: Associated Press.