Maryland: US President Barack Obama and First Lady Michelle departed for Oslo late Wednesday to accept his Nobel Peace Prize, an AFP photographer said.

The presidential plane known as Air Force One departed Andrews Air Force Base in Maryland, near Washington, bound for the Norwegian capital where Obama was to give a speech Thursday as a Nobel laureate.

The couple were to spend the night in Oslo before returning Friday to the United States.

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.Related article: Obama to address Afghan war paradox

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.