Updated

The top U.S. commander in Afghanistan downplayed expectations Wednesday of plans to withdraw American troops from the war-torn country starting next year and described a major policy review ordered by President Obama as little more than a "mid-course assessment."

General David Petraeus, in an interview with The Times of London, said Obama's deadline of July 2011 for the start of a drawdown would in fact be the start of a "process," and he reserved the right to set his own timetable based on conditions on the ground.

"It is not a date when we rush for the exit and reach for the light switch to turn it out before leaving the room," he said in Kabul.

His remarks came as a new book by journalist Bob Woodward exposed deep divisions within the Obama administration over U.S. goals in Afghanistan and whether the president's high-risk surge strategy can achieve them.

According to "Obama's Wars," the new commander-in-chief had to fight off requests from the Pentagon for more troops even after authorizing the deployment of 30,000 more U.S. soldiers.

The hybrid counter-insurgency strategy that he settled on was then attacked by his most senior civilian adviser, with Richard Holbrooke quoted as saying that the strategy "can't work".

The book also reveals that the CIA has created a 3,000-strong covert paramilitary Afghan force with orders to hunt Al Qaeda targets inside Pakistan as well as in Afghanistan.

Petraeus offered a staunch defense of the counter-insurgency strategy but admitted the campaign caused him frustration and impatience.

"I am conscious of the fact that the Afghan clock doesn't always move quite as rapidly as folks in other locations would like to see it move and as we would like to see it move," he said.

He is under pressure to demonstrate that his tactic of pouring additional forces into Afghanistan to fight the Taliban, secure the country and create a stable government is working.

"There are clocks in Washington and in London and other capitals that are also ticking rapidly. Our job obviously is to do the best we can to produce progress to show that this is the right approach and that it has the best prospect of achieving our important objectives here in Afghanistan."

Asked whether he was worried about waning public support for a war that has lasted nine years, Petraeus said: "We are obviously conscious of the strategic context in which we carry out this campaign.

"We feel the same frustration and impatience that citizens do ... but again I think we also recognize the importance of the mission here. There's no question between this mission and the link to September 11, 2001, or to the attacks in your country."