An aggressive Bush administration campaign to block arms sales to Iran has been dealt a series of setbacks by the refusal of some foreign governments to turn over alleged arms dealers arrested in undercover U.S. law enforcement stings.

In Thailand last month, authorities released from custody a high-ranking Iranian Air Force officer who had been caught in a sting mounted by U.S. Homeland Security and Defense Department investigators, who alleged that he was trying to buy missile-guidance devices. The release of the Iranian, Jamshid Ghassemi, was ordered by Thai courts, after the Iranian government argued to Thailand's government, that Ghassemi was the victim of American entrapment and that he would be tortured for confidential information about the Iranian military, if extradited to the United States.

In Britain, U.S. authorities have been having trouble finalizing the extradition to America of Nosratollah Tajik, a former Iranian ambassador to Jordan who was ensnared in a separate Homeland Security operation. During the course of this inquiry, Tajik allegedly sought to illegally export American-made night-vision devices to Iran.

In yet a third case, as NEWSWEEK first reportedChina last spring released an accused Iranian smuggler after he had been caught in another Homeland Security sting allegedly trying to buy American fighter-jet parts for shipment to Iran. The accused smuggler, Yousef Boushvash, had been at first detained by Chinese authorities in Hong Kong following the bust. But when the United States sought his extradition, Beijing officials ordered authorities to let him go, and Boushvash vanished, according to a U.S. official familiar with the case, who asked for anonymity due to diplomatic sensitivities.

These cases have frustrated Bush administration officials, who view the accused arms suppliers as part of a vast overseas network that is providing dangerous weapons to the Tehran regime. Though the arrests of the arms dealers do not involve alleged exports of nuclear technology to Iran, they are part of an extensive campaign by the White House to curb Iran's ability to obtain equipment which could be useful either for related military programs—such as its effort to develop longer-range missiles; or to its efforts to maintain and modernize its military forces, which have been decaying since the imposition of sanctions by the United States following the fall of the Shah in 1979.

Tehran is clearly playing hardball with Washington and foreign governments over these cases, U.S. officials believe. Details of arguments the Iranian government made to Thai authorities, in pressing for the recent release of the accused missile-parts smuggler Ghassemi, are contained in an affidavit obtained by NEWSWEEK which was submitted to the Thai courts earlier this year by the Iranian's defense lawyer, Kittipong Kiettanapoom.