LISBON, March 4: The United States is convinced that Dr A.Q. Khan sold nuclear secrets to Iran, Libya and North Korea without the approval of senior government officials in Pakistan, a top US arms control official said on Thursday.

"We have no reason to believe that President Pervez Musharraf or the top echelons of the Pakistani government were in any way involved with Khan," US Under secretary of State John Bolton told reporters in Lisbon where he is taking part in a two-day security conference.

"There may well be officials in the Pakistani government, military people, scientists, who were part of his network," he added. "But I distinguish between that and sanctioned approval, complicity, by the top levels of the Pakistani government as to which we have no evidence."

Mr Bolton said Washington could not rule out the possibility that Dr Khan and his network had made out nuclear sales to other countries or that the trafficking was still continuing.

"We do not know the extent to which other parts of the network may have survived, we are still investigating," he said. "There are reports that Khan was engaged with other countries and I wouldn't say these are reports that we feel we can confirm but it is obviously critical to try and understand the extent of his network's activities."

The under secretary praised Gen Musharraf, however, for taking what he described as 'important steps' to disrupt the network and make sure that the nuclear proliferation stops. -AFP