Foreign troops must carefully phase their withdrawal from Afghanistan ahead of an end-2014 deadline, Prime Minister David Cameron said on Saturday, after France suggested giving Afghan forces full responsibility for security in 2013.

I don't want to see some sort of cliff edge in 2014 when all of the remaining troops come out at once, Cameron said during talks in London with Afghan President Hamid Karzai.

But clearly, between now and 2014, the rate at which we can reduce our troops will depend on the transition to Afghan control in the different parts of Afghanistan...

French President Nicolas Sarkozy said on Friday France would pull its combat troops out at the end of 2013, a year before an end-2014 deadline fixed by the United States and its NATO allies for handing over responsibility for security to Afghan forces.

We have decided, in agreement with President Karzai, to call on NATO to give some serious consideration to the Afghan army taking full charge of NATO combat missions in the course of 2013, Sarkozy said at a news conference with Karzai in Paris.

He said he would raise this at a meeting of NATO defence ministers in Brussels on Feb 2 and 3.

However, some foreign troops, Sarkozy said, would stay on after 2013 to train the Afghan army - which western countries are building up with the aim of making it strong enough to maintain security without outside help after the end of 2014.

Foreign countries are already handing over responsibility for security in parts of Afghanistan to Afghan forces.

The idea of speeding up that transfer has been floated in the past, in part to provide a cushion to Afghan forces to take charge of security at a time when foreign troops would still be available to help in an emergency.

It was unclear whether Sarkozy's suggestion was meant merely to feed into this debate, or whether he was expecting the United States and its allies to agree to a serious acceleration in handing over to Afghan forces.

In Washington, U.S. defence officials said the United States, which has the lion's share of foreign troops in Afghanistan, was standing by NATO's goal of gradually handing over security responsibilities to Afghan forces by 2014.

That transition has begun, and we have made considerable progress toward this goal over the past year, thanks to the gains of the military surge and the development of Afghan security forces, Pentagon press secretary George Little said.

Consultations on transition would continue at the meeting in

Brussels next week, he said, ahead of a NATO summit due in Chicago in May.

A U.S. defence official said that, U.S. forces continue to plan to transition through to the end of 2014. Our policy has not changed.

In Brussels, a NATO spokeswoman echoed the Pentagon's comments, saying transition is well on track to be completed by the end of 2014, as we all agreed.

SUPPORT AFTER 2014

Foreign countries have promised to support Afghanistan with aid and advice for years after combat troops leave.

But they have scaled back their ambitions for Afghanistan to seek a minimum level of stability that would prevent the country from again becoming a haven for al Qaeda.

The United States also began talks with Taliban insurgents in late 2010 in a slow-moving process to try to reach, or at least begin to shape, a political settlement by the end of 2014.

With the western troop presence becoming increasingly unpopular inside Afghanistan, some officials have said the withdrawal of troops might make it easier to reach a settlement with insurgents - who use their opposition to foreign forces to rally support.

Cameron plans to pull out 500 British soldiers this year but has not yet set out a timetable for further withdrawals.

He made clear, however, that British combat troops would stay to the end of 2014 - though Britain has said it will not expand its area of operations in southern Afghanistan to fill in for departing troops from other countries.

We ... want to have a long-term relationship with Afghanistan, long after our combat troops come home, and that will happen at the end of 2014, he said.

Britain has some 9,500 troops in Afghanistan as part of the 130,000-strong NATO-led force. U.S. forces number some 90,000. France has 3,600 troops in Afghanistan.

Karzai and Cameron signed a partnership agreement setting out how their countries would work together after 2014.

Karzai said the agreement will take us into a future where Afghanistan will benefit from the assistance and cooperation and help of Britain towards becoming a fundamentally strong democratic state. The Afghan president was asked no questions at a tightly controlled media event.

(Additional reporting by Tim Castle in London, David Alexander in Washington, John O'Donnell in Brussels; Editing by Myra MacDonald)