An announcement on the date for transition to Afghan control is not expected until Nato‘s Chicago summit in May. Nato agreed at a previous summit in Lisbon in 2010 that home-grown forces would take the lead responsibility for security by the end of 2013, but there was some speculation today that this could be brought forward to the summer of next year.

Mr Cameron wants to ensure that the UK and US are “in lockstep” over the handling of the sensitive conclusion to an operation which will have lasted 13 years by the time international troops are pulled out.