Clare Short yesterday renewed claims that "regrettable" delays in the deployment of UK troops were a barrier to the humanitarian relief effort in Afghanistan.

The international secretary's second intervention on the issue in less than 24 hours has revived claims that the West's policy on ground forces for post-Taliban reconstruction in Afghanistan is in disarray.

Her comments undermined attempts by Tony Blair, during prime minister's question time, to assert that Britain was in "complete agreement" with the US on troop deployment.

Short's call for ground troops to carry out aid operations has been backed by a number of aid agencies concerned that a humanitarian disaster looms as winter draws in.

Downing Street has denied any postponement of UK troops, insisting that no decision has yet been taken to station the 6,000 soldiers currently on stand by.

The US has blamed "misunderstandings" with the Northern Alliance for delays but there is growing concern that there are transatlantic differences over a UK emphasis on "nation-building" and a continuing American focus on bringing Osama bin Laden and al Qaeda to justice.

A warning by US president Bush yesterday that the war in Afghanistan was not over, appeared to raise the imminent deployment of 1500 American marines.

"The most difficult steps in this mission still lie ahead," he said. "We have made a good start, yet there is still a lot to be done," he said.