The Pentagon says Afghanistan's Taleban leadership is at risk if it does not cooperate in the U.S.-led effort to kill or capture terrorist suspect Osama bin Laden, wanted in connection with last week's attacks in New York and Washington.

A senior U.S. defense official says the Taleban should take seriously President Bush's unconditional demand for the surrender of Osama bin Laden and the closure of all terrorist training camps in Afghanistan. The official, speaking on condition of anonymity, says if the Taleban ignores the ultimatum, it does so at its own peril.

The official's comments to VOA come amid reports that U.S. and British commando units have already begun moving into countries bordering on Afghanistan - the vanguard of a mass movement of U.S. ships, planes, and troops.

Pentagon officials will not comment on the reports, in line with their policy of not discussing operational or intelligence matters.

But intelligence and other sources indicate the Bush administration has been working to form what is described as a "floating coalition" in the region, a coalition believed to include the anti-Taleban Northern Alliance inside Afghanistan.

In a television interview, Friday on Fox News Channel, Defense Secretary Donald Rumsfeld says the alliance could be "a lot of help" in any U.S.-led military action. Mr. Rumsfeld suggests the alliance and other opponents of the Taleban could assist in reconnaissance and targeting.

Defense officials concede it will be difficult for U.S. forces to operate inside Afghanistan. But they say they have confidence in the ability of U.S. special operations units which are trained to work covertly in remote, inhospitable, and hostile areas worldwide.

Intelligence sources also remain convinced that Osama bin Laden remains holed up in Afghanistan, despite recent reports suggesting he has already fled the country.