UK troops in Afghanistan

James Arbuthnot, chairman of the defence select committee, said soldiers faced "very difficult circumstances".

The UK takes control of Nato forces in Afghanistan in May, with troops due to oversee reconstruction efforts.

One reason for a delay is a suggestion the Dutch government may go back on its offer to send 1,200 troops.

'Rule of law'

Mr Arbuthnot told BBC Radio 4's Today programme: "The question is, will there be enough troops to carry out, in very difficult terrain, against very difficult circumstances, even that amount of work?

"Will it be possible, given the surrounding circumstances in Afghanistan, to build democracy in an area which is overrun by warlords and where the rule of law is, as the Ministry of Defence official said [on Tuesday], rudimentary?"

Tony Blair has pledged to send 3,000 more troops to Afghanistan, most for Helmand province in the south, where the Taleban and drug traffickers are active.

Nato's International Security Assistance Force mission currently numbers about 9,200 troops, including 850 Britons.