David Cameron and Barack Obama insist that British and American troops are on course to step back into a support role from next year.

After talks in the White House, the Prime Minister and president said the international mission was entering its final stages ahead of the Afghans taking full responsibility for security in 2014.

Their confident pronouncements on Afghanistan came as both men lavished praise on each other and reaffirmed their commitment to the US-UK relationship, Mr Obama describing it as "essential", "indispensable" and "the strongest that it has ever been".

"There are some countries whose alliance is a matter of convenience but ours is a matter of conviction; two states... united for freedom and enterprise, working together day in, day out, to defend those values and advance our shared interests," Mr Cameron said.

At the press conference Mr Obama in turn described Mr Cameron as an "outstanding ally, partner and friend".

The PM and his wife Samantha were earlier welcomed to Washington with an extravagant ceremony at the White House.

On a sun-drenched South Lawn, packed with 7,000 guests - including children from both nations - Mr Cameron was given a 19-gun salute and a review of troops.

Mr Obama was emphatic about the enduring value of what he terms the transatlantic "essential relationship".

"Our world has been transformed over and over and it will be again," said the president.

"Yet through the grand sweep of history, through all its twists and turns, there is one constant - the rock-solid alliance between the United States and the United Kingdom."