American troops were last night gathering in Afghanistan as speculation grew that an all out attack on the last remaining Taliban stronghold of Kandahar was imminent.

Although waves of helicopters were said to be ferrying troops and armour to an airfield near the city, the Pentagon has refused to offically confirm the reports.

The arrival of what is expected to number approximately 1200 US troops marks a new phase of the conflict in Afghanistan. Prior to their landing, America's presence on the ground was limited to special forces whose primary mission is to locate Osama bin Laden.

The move came as British sources signalled that the government was set to revise plans for its 6000 forces who are on standby. Officials say the urgency of the situation had diminshed in recent days.