Obama says Nobel Peace Prize is "call to action"

The bestowal of one of the world's top accolades on Obama, who has yet to score a major foreign policy success after nearly nine months in office, was greeted with gasps from the audience at the announcement ceremony in Oslo.

Describing himself as surprised and deeply humbled, Obama said he would accept the award as a "call to action" to confront the global challenges of the 21st century.

"I do not view it as a recognition of my own accomplishments but rather an affirmation of American leadership on behalf of aspirations held by people in all nations," he said in the White House Rose Garden.

The Norwegian Nobel Committee praised Obama for "his extraordinary efforts to strengthen international diplomacy and cooperation between peoples," citing his fledgling push for nuclear disarmament and his outreach to the Muslim world.

Obama, a Democrat who took office as the first black U.S. president in January, has been widely credited with improving America's global image after the eight-year presidency of George W. Bush, who alienated both friends and foes with go-it-alone policies like the 2003 U.S.-led invasion of Iraq.

But critics called the Nobel committee's decision premature, given that Obama has achieved few tangible gains as he grapples with challenges ranging from the war in Afghanistan and the Israeli-Palestinian conflict to nuclear standoffs with Iran and North Korea.

Obama, told of the prize in a pre-dawn call from his press secretary, now also has the burden of living up to its expectations.