The United States has asked Pakistan, which is under tremendous pressure following an admission by its top scientist Abdul Qadeer Khan that he shared nuclear secrets with Libya, North Korea and Iran, to ensure that it does not become a source of proliferation again.

"We see Pakistan taking steps that go to that end," state department spokesman Richard Boucher said in Washington, DC on Thursday. "We see Pakistan developing information as part of an investigation that is useful to the whole international community to go after this private network, this network of people sharing materials, information and expertise. And we would expect them to share that information with the international community. Those are the important things."

Pakistan's Nuclear Bazaar

In an apparent disapproval of the presidential pardon to Khan, he said, "We would expect any country that is conducting an investigation to decide the appropriate penalties under their judicial system and their laws."

Asked whether pardoning a man who had transferred weapons-related technology to countries hostile to the US was appropriate, Boucher said, "I don't think it is a matter for the US to sit in judgement on… what is important in this case is really two things: One is that the network and the individuals who were doing this in Pakistan or from Pakistan be found out, stopped, prevented from making any such transfers again.

"... that the information that they develop is shared with the international community, because the international community as a whole needs to go after this network that extends far beyond Pakistan in some cases."