The United States is investigating new intelligence reports of contacts between Pakistani nuclear scientists and the Taliban and Osama bin Laden's terrorist network Al Qaeda.
American and Pakistani officials said they have received new reports of contacts involving scientists with actual experience in production of nuclear weapons and related technology.
Pakistan, a month earlier, had detained and interrogated two nuclear scientists who had contacts with the Taliban and Al Qaeda, but neither had any knowledge or expertise that would have helped terrorists build or obtain a nuclear weapon, officials said.
The intelligence report, US officials said was credible enough for them to focus new concern on the security of Pakistan's weapons programme.
Pakistani officials, however, said their government is resisting some of the American efforts to interrogate many scientists and engineers, as it could be Washington's ploy to learn the details of the country's secret nuclear programme.
They said the United States wants to question two other nuclear experts -- Suleiman Asad and Muhammed Ali Mukhtar, who have worked at two of Pakistan's most secret nuclear installations.
CIA Director George J Tenet discussed the issue with top officials while he was in the country last weekend, media reports said quoting Pakistani officials.
White House officials also said Tenet's trip was related in part to nuclear issues.
However, the two scientists were sent, shortly after September 11, on a vague research project to Myanmar and were not expected home soon.
Pakistan's military president, media reports quoting officials said, telephoned one of Myanmar's military rulers asking him to provide temporary asylum for the two nuclear specialists, and assured that they were not connected to terrorism.
A spokesman for Pakistan's Atomic Energy Commission said: "We don't want to interrupt them."
Washington is concerned that Al Qaeda is trying to obtain at least a primitive radioactive weapon and has concerns about the security of the Pakistani nuclear weapons programme, officials said.
Pakistani officials said they share Bush's concern but also believe that the United States is trying to leverage the current crisis to discover more about Pakistan's facilities, in case Washington wants to secure or destroy them.
American officials said, the Bush administration does not believe Al Qaeda has a nuclear weapon, despite its clear desire to obtain one.
But officials in Washington remain concerned that Al Qaeda cells elsewhere may be searching for enough material to make a 'dirty bomb', in which radioactive material would be wrapped around a conventional explosive and detonated, spreading nuclear contamination.
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