The long-awaited announcement of a US troop surge into Afghanistan is expected to be made next week by President Barack Obama.

News that a decision was imminent came after UK Defence Secretary Bob Ainsworth blamed the delay in unveiling extra troops for a decline in public support for the Afghan mission.

Mr Obama said the decision would be made public, but specified only that it would be after Thanksgiving on Thursday.

Speculation has mounted that he will unveil a surge of around 34,000 additional soldiers.

It is more than three months since the US administration began deliberating a report from the US commander on the ground, General Stanley McChrystal, which calls for an additional 40,000 troops.

Mr Ainsworth suggested that the delay in deciding whether to send more soldiers had made it harder to push the case for action.

Appearing in front of the Commons Defence Committee, he said the 98 British deaths this year were a key factor but said the "hiatus" in the US had not helped bolster public support.

He said: "We have suffered a lot of losses. We have had a period of hiatus while McChrystal's plan and his requested uplift has been looked at... and we have had the Afghan elections - which have been far from perfect, let us say - and all of those things have mitigated against our ability to show progress."

In Washington, Mr Obama gave his clearest indication yet that he was on the brink of making public his decision.

The US President refused to be drawn on actual date, only saying it would be "after Thanksgiving".