Khan, a national hero in Pakistan since he helped test the Islamic world's first nuclear bomb in 1998, confessed last month to passing on the nuclear secrets.

Powell, speaking over National Public Radio, said Pakistan's President Pervez Musharraf had only given a conditional pardon to Khan, stressing "conditional meaning that it can be taken away."

Musharraf offered the amnesty only after destroying Khan's network and forcing him to confess his illicit activity over local television, Powell said.

"But we came down very, very firmly with the Pakistanis on the need for them to help us and to help themselves totally pull up that network, and that's what the Pakistanis have done," he said.

"I do not think Dr Khan is enjoying the position he is in, and I will let the Pakistani government determine what else they should do with respect to Dr Khan," he added.

On the possibility of Pakistan allowing US officials to quiz Khan, Powell said "we are getting the information that we need, and I can assure you there is a good and a high level of cooperation between us and the Pakistani authorities on the questioning of Khan."

Musharraf has refused to allow an inquiry by international investigators, who want to probe further to determine whether the nuclear know-how was sold to other countries.

WAR.WIRE