At present there are 68,000 US troops in Afghanistan, attempting to maintain stability following Washington's 2001 invasion of the country to remove the Taliban, accused of harbouring al-Qaeda operatives, from power.

Stanley McChrystal, the chief US and Nato commander in Afghanistan, has requested 40,000 extra soldiers to add to the American personnel already in the country and the 40,000 Nato-troops also there.

Afghanistan recently has seen a peak in violence since the 2001 invasion and extra soldiers are said to be needed to battle opposition fighters and train local security personnel.

On Obama's past handling of the war, 48 per cent disapproved - a rise of one per cent from last month - while 45 per cent approved.

When considering whether the benefits of the war outweighed the costs, 52 per cent said that it was not worth fighting, against 44 per cent.

At least 841 US military personnel have died in the Afghan war, according to the defence department.