In addition to the deployments under way, McChrystal has also requested an extra 40,000 troops he says are necessary to prevent the country falling into the hands of the Taliban.

The Afghanistan president Hamid Karzai, today expressed support for McChrystal's request. "I'm fully behind him for what he's seeking in this report," Karzai told ABC's Good Morning America.

As part of the internal debate, the US defence secretary, Robert Gates, who is cautiously supporting McChrystal, is due to meet later today the vice-president Joe Biden, who is opposed to the troop increase and favours a shift in priority to tracking down al-Qaida in Pakistan.

A decision on McChrystal's troop request appears to have been postponed for a few weeks. Any extra troops will come as a result of a parallel reduction in the number of US troops in Iraq.

A US military planner told the Army Times: "We've increased forces in Afghanistan before we've reduced forces in Iraq in a meaningful way.

This surge will not be televised.