The foreign intelligence official said high-ranking North Korean military personnel have been seen at some of Iran's nuclear installations. A hotel is reserved for North Koreans in Tehran and a resort on the Caspian Sea coast northwest of Tehran has been set aside for their use, according to one of the sources and a U.N. official.
The centrifuges seen by IAEA officials at Natanz in February were based on a Pakistani design, according to intelligence officials. The design and other new evidence point to Pakistan as a bigger supplier of nuclear weapons technology to Iran than initially thought, said foreign intelligence officers, Iranian exiles and independent experts.
While U.S. intelligence is aware of Pakistan's help to Iran, the Bush administration has not pushed the issue with Islamabad because of Pakistan's role as an ally in the battle against the Al Qaeda terrorist network and Afghanistan's Taliban, outside experts and foreign intelligence officials said.
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Signs of Pakistani Aid
The most convincing sign of Pakistan's role in Iran comes from what several people described as the long involvement in Iran of Khan, the scientist regarded as the father of Pakistan's nuclear bomb.
The CIA concluded in a top-secret analysis last year that Khan shared critical technology on centrifuges and weapons-test data with North Korea in the late 1990s. The agency tracked at least 13 visits by Khan to North Korea over a span of several years, according to a January article in the New Yorker magazine.
Two former Iranian officials and American and foreign intelligence officials said Khan travels frequently to Tehran to share his expertise. Most recently, two of these people said, he has worked as a troubleshooter to iron out problems with the centrifuges and with weapons design.
Ali Akbar Omid Mehr, who was in charge of Pakistani affairs at Iran's Foreign Ministry in 1989 and 1990, said he came across Khan as he prepared what is known as a "green book" detailing contacts between Tehran and Islamabad.
"I saw that Mr. A. Q. Khan had been given a villa near the Caspian Sea for his help to Iran," Mehr said in an interview in Denmark, where he and his family live under assumed names since he defected in late 1995.
His account of the villa was supported by other Iranian exiles.
Khan might have played a role in a previously undisclosed offer from Pakistani military commanders to sell nuclear weapons technology to Iran in 1989, two former senior Pakistani officials said in separate interviews describing the episode.
