The International Atomic Energy Agency said Iran had not told the IAEA it had designs for sophisticated "P-2" centrifuges for enriching uranium nor that it had produced polonium-210, an element which could be used as a "neutron initiator (to start the chain reaction) in some designs of nuclear weapons."
This was despite Iran's claim last October that it had given the IAEA a full picture of its nuclear program.
IAEA chief Mohamed ElBaradei told reporters Tuesday on a flight from Tripoli to Vienna: "I hope this will be the last time that any aspect of the program has not been declared to us."
He said that since October: "We have seen some good cooperation from Iran, particularly with regard to access to sites."
But he said he wanted to see "more prompt, detailed information coming from Iran."
He called the failure to report the P-2, a gas centrifuge design that Iran got through a global black market from Pakistan, a "setback."
The IAEA report said an Iranian scientist has confirmed experiments with polonium but Tehran has offered an explanation involving the material's civilian uses, such as in power generation.
The report is to be reviewed when the IAEA's 35-nation board of governors meets March 8 to rule both on Iran's cooperation and Libya's effort to dismantle programs to develop weapons of mass destruction.
The United States, which charges Iran with secretly developing nuclear weapons, has called for the IAEA to refer Iran to the UN Security Council for possible sanctions. Iran says its nuclear program is strictly peaceful.
Diplomats said the United States would almost certainly not have backing for sanctioning Iran when the board meets since European nations still want to give Iran a chance to cooperate.
The report said Iran had, only hours before the report was issued, promised to suspend all activities related to uranium enrichment, including "the assembly and testing of centrifuges."
Iran had previously suspended uranium enrichment but was still making centrifuges.
A senior official close to the IAEA said this wider suspension "only came as a result of very intensive discussions" by European countries.
Britain, France and Germany had in October struck a deal with Iran to cooperate with the IAEA, and are still stressing the path of "constructive engagement," a Western diplomat said.
The report also said Iran's program had striking similarities to Libya's as they were both supplied by the same black market, run by the disgraced former head of Pakistan's nuclear program Abdul Qadeer Khan.
The report said the jury was still out on Iran's claim that traces of highly-enriched uranium (HEU) found at its nuclear facilities at Natanz and the Kalaye Electric Company were from equipment bought on the black market and contaminated with HEU.
The IAEA said the types of uranium differ, even though Iran insists that the source in both cases was the same imported centrifuge components.
"The agency continues to work with the country from which the components are believed to have initiated with a view to resolving the issues associated with the contamination," the report said.
The senior official said this country was Pakistan, but that no agreement had yet been reached for agency inspectors to travel there to take environmental samples to test for traces of uranium.
In Tehran, Iran's main conservative party, set to lead parliament after sweeping elections, vowed Tuesday to continue to show "goodwill" to the IAEA, but reiterated that the country had a right to nuclear technology.
Iran's foreign ministry has said repeatedly that it does not know the source of the nuclear technology it bought.
But Malaysian police on Friday declared that Khan had sold nuclear centrifuge parts to Iran in the mid-1990s.