President Barack Obama has said the US must uphold moral standards when waging wars that are necessary and justified¹, as he accepted his Nobel Peace Prize.

奥巴马在接受诺贝尔和平奖的时候，宣称美国发动战争必须坚持必要和理由充分的道德标准。

In his speech in Oslo, he defended the US role in Afghanistan, arguing the use of force could bring lasting² peace.

He also said his accomplishments³ were slight compared with other laureates桂冠诗人，得奖者.

Mr Obama was given the prize in October for his "extraordinary efforts to strengthen international diplomacy⁴ and co-operation between peoples".

Thursday's ceremony in the Norwegian capital came days after Mr Obama announced he was sending 30,000 extra US soldiers to the war in Afghanistan.

There was a mixed reaction when he was named as the winner of this year's prize, becoming the fourth US president to be given the honour.

Mr Obama's elevation海拔，提高 to the rank of fellow laureates such as Nelson Mandela, Mother Teresa and Martin Luther King, before he has even spent a year in office, has sparked fierce debate.

Critics also said it was inappropriate for the honour to go to the commander-in-chief of a country involved in conflicts in Iraq and Afghanistan.

Acknowledging the controversy争论，辩论, Mr Obama said he accepted the award with humility⁷, adding: "Compared to some of the giants of history who have received this prize... my accomplishments are slight."

He could not argue with those who said many previous laureates were "far more deserving" of the honour than him, he said.

Defending his Afghan troop deployment⁸, Mr Obama said there were times when "the use of force [was] not only necessary but morally justified," as long as force was proportionate成比例的 and civilian⁹ casualties人员伤亡 minimised.

"Instruments of war do have a role to play in preserving the peace", he said.

"A non-violent movement could not have halted Hitler's armies," he added. "Negotiations¹⁰ cannot convince al-Qaeda's leaders to lay down their arms."

He said the US "must remain a standard bearer倡导者，旗手 in the conduct of war" to differentiate¹¹ it from "a vicious堕落的，恶毒的 adversary¹²对手，敌手 that abides¹³ by no rules".

Mr Obama also emphasised alternatives to violence, stressing the importance of diplomacy and sanctions制裁，处罚 to confront nations like Iran and North Korea over their nuclear programmes.

While Russia and America were working to reduce their nuclear stockpiles库存，储备, he said the international community must ensure Tehran and Pyongyang did not "game the system".

"Let us reach for the world that ought to be," Mr Obama said. "We can understand that there will be war, and still strive for peace."

He paid tribute to anti-government demonstrators in Iran, Burma缅甸 and Zimbabwe津巴布韦, and said the US would always stand on the side of those who sought freedom.