It's impossible to keep Gordon Brown's promise of cutting troops in Iraq this year, says Jock Stirrup

Bringing troops home from Iraq will not begin to happen until next year, the head of the Armed Forces said.

Gordon Brown had said the numbers would be cut to 2,500 this year but Air Chief Marshal Sir Jock Stirrup said that was no longer possible.

The Chief of the Defence Staff pledged however that from 2009, the numbers kept in Iraq would be lowered to give soldiers more of a break between tours of duty.

With around 4,000 troops in Iraq and 8,000 in Afghanistan, he said the forces were not structured to maintain two operations on such a scale for an extended period.

'I would expect us to see further substantial progress towards a more sustainable tempo in the course of the next year,' he told BBC1's The Andrew Marr Show.

He said the delay in reducing numbers in Iraq was, 'caused by a number of factors, the principle one of which is that we trained the 10th Division of the Iraqi Army in Basra, but then the Iraqis decided to move the 10th Division out of Basra and form a new division, the 14th Division, and we are now busy training and mentoring that one.'

Experts suspect it could take until 2010 for the last soldiers to return from Iraq.

On Afghanistan, the defence chief said Britain's military commitment would continue for 'a few years'.

To help the forces, the Government is to offer free places at university for soldiers, sailors and airmen after six years' service.