British ground troops are inside Afghanistan providing assistance to Northern Alliance fighters, Defense Secretary Geoff Hoon said Sunday, confirming the presence of British forces in the country for the first time. 

"I can certainly confirm that there are members of Britain's armed forces on the ground in northern Afghanistan liaising with the northern alliance providing advice and assistance," Hoon told British Broadcasting Corp. radio. 

The Ministry of Defense would not give details about the troops or say how many were in Afghanistan. 

Last month Britain announced that 600 special forces troops would be available for operations in Afghanistan. The plans called for 200 Royal Marine commandos operating from two assault ships in the region, with 400 men from the same unit on standby in Britain. 

The commandos are trained to mount raids, operate behind enemy lines and fight in mountainous and arctic territory, and Hoon suggested last month that plans called for sporadic strikes by small, elite units. 

Earlier Sunday, Hoon said the use of allied ground troops was an important part of the U.S.-led military campaign in Afghanistan. 

Hoon said the Northern Alliance — which has captured the city of Mazar-e-Sharif claims to have made other major advances in the north — "have played their part, and they are continuing to play their part. 

"Bombing is another part, the use of coalition forces on the ground is a further part," Hoon told the BBC's Breakfast With Frost program. 

He also said he believed Usama bin Laden possessed material that could contributing to a nuclear weapon. U.S. and British officials say bin Laden has sought to acquire nuclear, chemical and biological weapons. 

"We are certainly aware that he has some material that could contribute to a nuclear weapon," Hoon said. "We are not convinced at this stage that he is capable of producing a nuclear bomb."