U.S. Ambassador to Pakistan Ryan Crocker tells VOA that Islamabad has done a good job in breaking up Abdul Qadeer Khan's illegal nuclear black market network.
"The steps taken by the government of Pakistan to dismantle the A.Q. Khan network and to set in place the safeguards to ensure that that kind of activity never takes place again are certainly most welcome," he said.
But he adds that the full extent of the illegal sales have yet to be determined.
"They continue to pursue the investigation into the activities of A.Q. Khan,” he added. “It is very important that they do so because we don't think that all the answers are in yet. The government of Pakistan has undertaken that they will fully share anything that they learn with us. And I think that it is very important that they keep at this."
Mr. Khan is considered a national hero in Pakistan for helping the country to become a nuclear weapons power.
Last year he shocked the nation as well as the world by admitting publicly to have illegally sold nuclear technology to Iran, Libya and North Korea.
The government pardoned him, citing his contribution to improving Pakistan's national security, but has since kept him under house arrest. Some of his associates have been charged in connection with the Khan network.
The United Nations nuclear watchdog group, the International Atomic Energy Agency, has repeatedly asked Pakistan to allow U.N. investigators to question Mr. Khan to determine the extent of his network. The United States has also reportedly asked for similar access.
Pakistan, however, has so far refused both parties, noting that it has no treaty obligation to allow them to interview Mr. Khan.
But Ambassador Crocker says that so long as the Pakistani investigation produces results, it is not important who is allowed to interrogate Mr. Khan.
"The important thing is not the identity of the questioner,” he said. “It's keeping at this with the right questions until we all agree that we have all the right answers."
Critics of the Pakistani government maintain the nuclear proliferation could not have taken place without the involvement of top military officers. However, officials deny these claims.