WASHINGTON – A US intelligence report assesses that Iran encountered roadblocks that slowed the advance of its nuclear program in 2011, even as the Islamic Republic continued to expand its nuclear infrastructure and supply of enriched uranium.“Although Iran made progress in expanding its nuclear infrastructure during 2011, some obstacles slowed progress during this period,” according to an unclassified CIA report presented to Congress this week. It did not specify what those obstacles were or how greatly they had set back the program.Iran’s ballistic missile program – “its primary deterrent,” according to the CIA – includes ever more short- and medium-range missiles. “Iran’s ballistic missile inventory is one of the largest in the Middle East,” the review found.However, the report said that while the country was making strides in its missile and satellite program, it must still rely on outsiders.“Iran continued to move toward self-sufficiency in the production of ballistic missiles, but almost certainly remains dependent on foreign suppliers for some key missile components,” the report stated. “Entities in China and Russia along with North Korea are among likely suppliers.”The report also found that during this time, Iran had continued to increase its enrichment of uranium at the underground facility in Natanz, as well as in testing and operating advanced centrifuges.While the number of centrifuges dropped from around 8,900 to 8,000 in the last year, those reported as operating jumped from 3,800 to 6,200. The amount of lowenriched uranium Iran produced, meanwhile, also increased more than 50 percent, from 3,200 to 4,900 kilograms. Of that, some 80 kg. is believed to be at the 20%-enriched level. The growth in centrifuges and 20% enrichment occurred at the underground Fordow site as well.The report also surveyed Iran’s development of ballistic missiles and chemical and biological weapons, the latter of which Tehran is believed to be able to produce if so chooses.