The US has replaced its top general in Afghanistan as President Barack Obama tries to turn around a stalemated war.
US defence secretary Robert Gates said he asked for the resignation of General David McKiernan.
Mr Gates said new leadership is needed as the Obama administration launches its strategy in the seven-year-old campaign.
The change is aimed at "getting fresh thinking, fresh eyes on the problem", he said.
The move comes as more than 21,000 additional US forces begin to arrive in Afghanistan, dispatched by Mr Obama to confront the Taliban more forcefully this spring and summer.
Replacing Gen McKiernan will be Lieutenant General Stanley McChrystal, who has had a top administrative job at the Joint Chiefs of Staff for less than a year. He is a former commander of the Joint Special Operations Command.
Gen McKiernan held the command in Afghanistan for about 11 months.
Mr Gates recommended to Mr Obama that Lt Gen McChrystal be nominated for the top job and that Lt Gen David Rodriguez be his deputy. He urged the Senate to confirm the two quickly.
Mr Obama approved 17,000 additional combat forces for Afghanistan this year, plus 4,000 trainers and other non-combat troops.
By year's end, the United States will have more than 68,000 troops in the huge country - about double the total at the end of George Bush's presidency but still far fewer than the approximately 130,000 still in Iraq.
