The U.S. and South Korea believe Iranian missile experts secretly entered North Korea recently and are staying near the North's rocket launch pad in Tongchang-ri.
"Identifiable cars have been spotted traveling back and forth from the quarters to the missile launch site," a government source here said. "We believe they're carrying Iranian experts."
North Korea apparently invited Iranian missile experts to help with technical problems after the previous rocket launch in April failed.
The rocket launches are widely seen as a cover to test long-range ballistic missile technology.
UPI said experts from Iran's Shahid Hemmat Industrial Group, which developed the Shahab-3 intercontinental ballistic missile, will be present at the North Korean launch. "The missile connection between North Korea and Iran, which started in the 1980s, appears to be more extensive than expected," said a government official here.
North Korea and Iran began cooperating in the development of missiles and other weapons of mass destruction in the 1980s, when Tehran asked Pyongyang help in developing missile technology to counter attacks from Iraqi Scuds.
In 1987, Iran imported 100 Scud-B missiles with a range of 300 km and 12 mobile launch vehicles from North Korea and used them against Iraq.
Since then, North Korea has exported Scud-C (1992) and Rodong missiles (1994) to Iran and also dispatched experts to Iran in 1990 to help it build its own missile manufacturing plant. In 1997, the North provided computer software to Iran to produce Rodong missiles.
Experts believe Iran's Shahab-3 was based on North Korea's Rodong missile, which has a range of 1,300 km, while the Shahab-5 and Shahab-6 were modeled after the North's Taepodong-2 missile.
Iran succeeded in putting satellites into orbit in February 2009 and February this year using rockets based on the Shahab missile.
Iran is now apparently returning the favors. "Iran obtained missile technology not only from China and Russia but also from Western countries such as Germany and the U.K.," said one rocket expert at a state-run research institute here. "All that missile technology ended up in North Korean hands."
A Defense Ministry official here said tight sanctions from the international community prompted North Korea to test a ballistic missile in Iran.