The report was prepared by a member nation of the International Atomic Energy Agency and given to AP on the condition that the country not be identified because of the confidential nature of the information.
The reports claims Teheran is willing to pay $450 million for the shipment and added that "the price is high because of the secret nature of the deal and due to Iran's commitment to keep secret the elements supplying the material".
Clandestine imports are banned by the UN Security Council, and Iran is currently under sanctions that ban the importat of all items, materials, equipment, goods, and technology that could contribute to its enrichment activities.
A Western diplomat from a member of the IAEA's 35-nation board said the report was causing "concern" among countries that have seen it and generating "intelligence chatter".
A senior US official told the AP that Washington was aware of the intelligence report but declined to discuss specifics:
We are not going to discuss our private consultations with other governments on such matters but, suffice to say, we have been engaged with Kazakhstan and many of our other international nonproliferation partners on this subject in particular over the past several years. We will continue to have those discussions.
State Department spokesman Ian Kelly said: "The transfer of any uranium yellowcake ... to Iran would constitute a clear violation of UNSC sanctions. We have been engaged with many of our international nonproliferation partners on Iran's illicit efforts to acquire new supplies of uranium over the past several years."
Purified ore, or uranium oxide — known as "yellowcake" — is processed into a uranium gas, which is then spun and re-spun to varying degrees of enrichment. Low enriched uranium is used for nuclear fuel, and upper-end high enriched uranium for nuclear weapons.
Kazakhstan is among the world's three top producers of uranium, accounting for more than 8,500 tons last year. In comparison, Iran produces only an estimated 20 tons a year.