Iran and North Korea have made significant progress in a joint effort to develop ballistic missiles, the head of the Pentagon's Missile Defense Agency said on Thursday. "It really is an international effort going on out there to develop ballistic missile capability between these countries," Reuters quoted US Army Lieutenant General Patrick O'Reilly as telling a forum on Capitol Hill. "We've seen it for years and it continues," he said of such cooperation between North Korea and Iran, whose Shahab missiles are widely reported to be based on North Korean designs. The Jerusalem Post could not independently confirm the report. According to the report, O'Reilly said that the two countries are sharing know-how on avionics, propulsion and materials, among other things and described the ability to fire missiles with a stable ignition and launch a second stage as "a significant step forward" for both Teheran and Pyongyang. When asked whether North Korea or Iran were further ahead in missile development, the head of the Pentagon's Missile Defense Agency said it could be described as a "horse race" with no clear leader. In related news, Reuters reported that the US Air Force's National Air and Space Intelligence Center says that Iran, with support from outside sources, could produce a missile capable of hitting the United States within six years. "Iran has ambitious ballistic missile and space launch development programs and, with sufficient foreign assistance, Iran could develop and test an ICBM capable of reaching the United States by 2015," the US center said in a new report. North Korea is continuing work on its Taepodong 2 "that could reach the United States with a nuclear payload" if developed as an intercontinental ballistic missile, the report claimed.