U.S. President Barack Obama on Thursday accepted his controversial Nobel Peace Prize "with deep gratitude and great humility" while acknowledging his few accomplishments and delivering a firm defense of war.

Nobel Peace Prize laureate, U.S. President Barack Obama holds his diploma and medal during the Nobel Peace prize awarding ceremony at the City Hall in Oslo, capital of Norway, Dec. 10, 2009. [Zhuang Yuwei/Xinhua]

"I am at the beginning, and not the end, of my labors on the world stage," Obama said in his 36-minute speech. "Compared to some of the giants of history who have received this prize ... my accomplishments are slight."

The Norwegian Nobel Committee's decision to give this year's peace prize to the president sparked questions worldwide ever since it was announced on Oct. 10.

In awarding the prize to Obama, the Nobel panel cited his call for a world free of nuclear weapons, for a more engaged U.S. role in combating global warming, for his support of the United Nations and multilateral diplomacy, and for broadly capturing the attention of the world and giving its people "hope."

Just nine days after ordering 30,000 additional U.S. troops into battle in Afghanistan, Obama refused during the speech to renounce war for America or under his leadership. He said he faces the world as it is and that he is obliged to protect and defend his country.

Nobel Peace Prize laureate 2009, U.S. President Barack Obama (1st L, top right) attends the Nobel Peace prize awarding ceremony at the City Hall in Oslo, capital of Norway, Dec. 10, 2009. [Zhang Yuwei/Xinhua]

"A nonviolent movement could not have stopped Hitler's armies," the president said, "Negotiations cannot convince al-Qaida's leaders to lay down their arms. To say that force is sometimes necessary is not a call to cynicism, it is a recognition of history."

Earlier in the day, Obama, at a joint press conference following his talks with Norwegian Prime Minister Jens Stoltenberg, said that by July 2011 there would be a definite shift in the ground situation in Afghanistan.

Small groups of protesters chanted slogans outside of the hall where Obama spoke as helicopters hovered over Oslo.

The protesters called on the White House to change its reluctance on actions to combat climate change and urged an end to the war in Afghanistan.

Obama shortened his stay in Oslo from the usual three days of celebration to just 26 hours and was scheduled to leave Oslo to return to Washington on Friday morning.

Of the traditional activities that associate with the Nobel Peace Prize awarding, Obama would only observe the torchlight procession from the balcony of the Grand Hotel room where he spent just one night in Oslo.

The president bypassed the traditional luncheon given by Norwegian King Harald V in honor of the Nobel Peace winner and a visit to the Peace Center where an exhibition of photos depicting his life was on display.

The Nobel award comes with a 1.4 million-U.S.-dollar prize. The White House said Obama will donate that to charities but has not yet decided which ones.