US President Barack Obama will dwell on the sombre paradox of waging war in Afghanistan even as he is lauded as a man of peace on Thursday when he accepts his surprise Nobel prize in Norway.

After less than a year in power, with few defining foreign policy wins and with his once soaring popularity fading at home, Obama faces a sensitive political assignment during a day of solemn ceremonies in Oslo.

NONE White House director of speechwriting Jon Favreau told AFP that Obama would speak solemnly about the odd coincidence of accepting the revered prize a week after ordering 30,000 troops to Afghanistan in a major war escalation.

"The president is receiving a peace prize as the commander in chief of a nation that is in two wars," said Favreau, one of two White House speechwriters working on the text with Obama.

Obama was expected to put the finishing touches on his speech as he flies across the Atlantic overnight before a day of ceremonies in Oslo, protected by the biggest ever security operation rolled out by the Norwegian government.

With many critics suggesting that Obama's resume is too thin to stand scrutiny with other Nobel peace laureates, the president will also seek to deflect attention from himself, aides said.

"He sees this as less of a recognition of his own accomplishments and more of an affirmation of a desire for American leadership in the 21st century," Favreau said.

Pro-engagement foreign policy

Obama will, as often before on foreign trips, seek to address divergent audiences: abroad, where he is highly popular and in the United States, where domestic critics say his pro-engagement foreign policy has yielded little.

Many Americans, and even some Obama supporters abroad, appear to doubt that the president deserves a prize awarded in the past to Nelson Mandela, the Dalai Lama and Aung San Suu Kyi.

A Quinnipiac University poll this week found by a wide margin, 66-26 percent, that Americans believe Obama does not merit the prize.

"It's probably a good thing for President Obama that the time difference from Norway means the Nobel presentation will occur while most Americans are sleeping and might get less coverage in the United States," said Peter Brown, assistant director of the Quinnipiac University Polling Institute.

The White House took a humble line on Wednesday, with spokesman Robert Gibbs saying that Obama believed his achievements should not be mentioned in the same light as those of past peace laureates Mandela and Mother Teresa.

Future greatness

Like Obama, the Nobel committee had to defend itself over the prize, arguing that it is intended to spur the president to future greatness than a recognition of a complete legacy.

NONE The committee lauded Obama for "extraordinary efforts to strengthen international diplomacy and cooperation between peoples."

"The Committee has attached special importance to Obama's vision of and work for a world without nuclear weapons," and the president was credited with creating a "new climate" of "multilateral diplomacy in international politics."

Obama advocates counter that he is driving towards a new treaty on nuclear arms cuts with Russia, and offered to rebuild US ties with Islam in a major speech to the Muslim world.

He offered an open hand to Iran, which appears to have been spurned, is engaging North Korea and Myanmar and transformed US policy on global warming.

Obama is the third sitting US president to win the peace prize, after Theodore Roosevelt in 1906 and Woodrow Wilson in 1919.