Iran advanced its missile development with the help of North Korea, and the Middle Eastern nation may still rely on the communist nation for materials necessary for producing its ballistic missiles, a congressional report has said.

The Congressional Research Service raised the suspicion in a recent report, noting that the intelligence community assessed until the latter 2000s that North Korean cooperation with Iran's ballistic missile program was ongoing and significant.

"Iran has likely exceeded North Korea's ability to develop, test and build ballistic missiles. But Tehran may, to some extent, still rely on Pyongyang for certain materials for producing Iranian ballistic missiles, Iran's claims to the contrary notwithstanding," the report said.

"For example, some observers argue that Iran may not be able to produce even its Scud B and Scud C equivalents -- Shahab-1 and Shahab-2, respectively -- without some foreign support for key materials or components," it said.

Nevertheless, however, Director of National Intelligence James Clapper stated during a Senate Armed Services Committee hearing in 2014 that Iran is not currently receiving assistance with its ICBM program. Clapper also said in February this year that there has "not been a great deal of interchange" between Iran and the North, it said.

The report said Syria continues to rely on North Korean and Iranian assistance for its missile program, noting that Defense Intelligence Agency Director Michael Flynn testified in 2013 that Syria's liquid-propellant missile program -- Scud B, Scud C and Scud D missiles -- depends on "essential foreign equipment and assistance, primarily from North Korean entities."

On suspected nuclear cooperation between Iran and North Korea, the report said that the official U.S. assessment has been that there is no such cooperation between the two countries, even though some press reports have pointed to alleged cases of nuclear cooperation, such as the possibility of Iranian officials witnessing North Korean nuclear tests. 

"U.S. officials have stated publicly that there is no nuclear cooperation between Iran and North Korea," the report said.

"Knowledgeable current and former U.S. officials contacted by CRS said that they were unaware of official unclassified U.S. government evidence of nuclear cooperation between Iran and North Korea."

But the report cited then-Director of National Intelligence Dennis Blair saying in 2009 that Pyongyang could attempt to transfer nuclear technology and material across its border.

"Pyongyang probably also perceives that it would risk a regime-ending military confrontation with the United States if the nuclear material was used by another country or group in a nuclear strike or terrorist attacks, and the United States could trace the material back to North Korea," Blair was quoted as saying.

"The North might find a nuclear weapons or fissile material transfer more appealing if its own stockpile grows larger and/or it faces an extreme economic crisis where the potentially huge revenue from such a sale could help the country survive."  (Yonhap)