US President Barack Obama has said enough progress is being made in Afghanistan to begin withdrawing US troops in July.
Mr Obama insisted that US-led forces were scoring gains against the Taliban and al-Qaeda but warned they were fragile and reversible.
He said the United States was on course to meet his pledge to begin withdrawing troops by mid-2011 and transition to full Afghan security control by 2014 - a timetable Britain is also supporting.
"I want to be clear, this continues to be a very difficult endeavor," the president said at the White House as he unveiled a review of his year-old strategy. But, he added, "We're on track to achieve our goals."
His defense secretary, Robert Gates, said it was too early to say how quickly troops would be withdrawn, but Washington hoped to accelerate the drawdown as more progress was made. There are about 100,000 US troops in Afghanistan.
David Cameron said the review "is consistent with the British government's assessment and strategy, and with the agreements made by the international coalition and the Afghan government at the Lisbon NATO Summit".
He added: "We also agree that we must use our civilian and military momentum to support a durable and favorable political resolution of the conflict.
"Like President Obama, we see 2011 as the year in which we have to make progress both lasting and irreversible."