British commanders believe that the Afghan National Security Forces (ANSF), the Army and police, are not yet fully capable of taking over from international forces.
Under current plans the ANSF are supposed to take over responsibility for security by the middle of 2013 and all International Security and Assistance Force (ISAF) troops will be withdrawn from combat operations by the end of 2014.
The timing has been agreed by David Cameron and Barack Obama, and would mean that Britain’s current deployment of 9,000 soldiers would be reduced significantly next year, and that after 2014 only a small number of UK forces would remain in Afghanistan, mostly as advisers to the Afghan military.
But late last month Philip Hammond, the Defence Secretary, said the timetable could be speeded up, if America judged it safe.
“We haven’t yet decided what the profile of the draw-down is going to be between this autumn and the end of 2014.
"That is something we will look at towards the end of this year when we understand better what our allies in Afghanistan are planning.”
However Mr Cameron has now been advised that there are significant fears over the quality and ability of Afghan troops, who are supposed to gradually take over control from ISAF (International Security and Assistance Force) soldiers next year.
Concerns over the ANA have been growing, and aired in public before.
By the end of 2014, the Afghan Army must reach a level of 240,000 troops, more than twice the size of the British Army, which will give the combined Afghan National Security Forces a total strength of around 352,000. Crucially, those troops and other members of the security force must also be able to operate entirely independently before ISAF troops leave.
However, sources said that the current rate of desertions and concerns over the quality of the soldiers who remain meant that there are grave doubts over that timetable. One particular concern is that there are desertions not just because soldiers are going home, but because they are changing sides to the Taliban, taking with them arms and expertise gained in training.
The discussions with Mr Cameron this summer came after Gen Sir Peter Wall, the head of the Army, was publicly rebuked by the Prime Minister last year when he suggested that Britain’s withdrawal should be linked to conditions on the ground rather than a political timeline.
An MOD spokesman said: “Transition to an Afghan security lead is now well under way and Afghan forces will soon be responsible for areas covering 75% of the country’s population.
"It is the Afghans who are increasingly taking the lead on operations, deploying in formed units, carrying out their own operations and taking greater responsibility for security both across Afghanistan and in Helmand where UK Forces operate alongside side them.
“UK forces will draw-down by 500 to 9,000 this year and will cease combat operations by the end of 2014 when the Afghans will take the overall lead.