OSLO: President Obama, who earlier arrived in Norway with his wife Michelle, also defended the US record in Afghanistan and his planned surge of 30,000 military personnel as motivated by his desire to bring peace to the war-torn country.

In his acceptance speech, he hit back at critics of his plan to begin withdrawing US soldiers from Afghanistan in mid-2011, saying he was “unambiguous” about the date and would debate it no further.

But he struck a modest note when he said others may be “more deserving” of the prestigious prize this year.

Shortly before his own investiture as a Nobel laureate, Obama marvelled at the “galvanising” impact of the US civil rights leader Martin Luther King.

President Obama and wife went directly to the Norwegian Nobel Institute to sign the guest book after flying into tightly secured Oslo for a day of events marking the first-year US president’s surprise Nobel prize.

“Michelle and I were commenting on the fact that when Dr King won his prize it had a galvanising effect around the world, but also lifted his stature in the United States in a way that allowed him to be more effective,” US President said.

He said he was honoured to receive the peace prize, and had paid tribute to the work of the Nobel committee in the guest book.

“I think it’s important to congratulate the Nobel Committee for the work that it’s done over the course of history to highlight the cause of peace, but also to give voice to the voiceless and the oppressed around the world.”

Martin Luther King won the Nobel peace prize in 1964. Obama has often said that he owes part of his success in becoming the first black US president to the legacy of the civil rights leader.