Britain is expected to send about 1,000 soldiers to join US-led raids on Afghanistan, according to British defence sources.
Most of the troops, many of whom are on exercises in Oman, would be used to help secure bridgeheads or bases to be used in raids against Taliban forces, newspaper reports say.
The deployment is expected to include members of the Special Air Service (SAS), Parachute Regiment, Royal Marine Commandos and the Gurkhas.
Defence sources said talks were ongoing over the deployment of the Parachute Regiment or the Royal Marines to protect any SAS-led operation.
British support for the United States in the first two weeks of the strikes has largely been restricted to mid-air refuelling and air reconnaissance. Submarines have fired Tomahawk cruise missiles twice.
But analysts believe some SAS soldiers are in Afghanistan, working with the Northern Alliance, gathering intelligence and picking targets.