The International Atomic Energy Agency has criticized Iran for hiding nuclear activities, but put off sending the matter to the United Nations Security Council.
A special session of the IAEA board of governors met Saturday to break a week-long deadlock over Iran's nuclear program.
Canada, Australia and Ireland presented a U.S.-backed text that was opposed by non-aligned countries and Russia and China.
In a compromise move, the western countries dropped moves that could have sent the issue to the U.N. Security Council for possible sanctions. But the resolution puts pressure on Tehran to come clean on its nuclear activities.
Iran reacted angrily to the resolution, saying the United States had imposed its will on the board.
The latest IAEA report, presented to the board Monday, said Iran had hidden advanced centrifuges that could be used in a weapons program. It claimed that most of the workshops were located in military industrial locations and not in the energy sector.
The United States held that this was evidence of a nuclear weapons program, something that Tehran strongly denies. The U.S. ambassador to the IAEA, Kenneth Brill, says the resolution passed Saturday is not the end of the matter.
"There are a large number of very significant outstanding issues that still need to be dealt with," he said. "But this issue - the Iran nuclear program issue, for the IAEA board of governors, will be a long term issue, because there's more to go to get to the bottom of it."
For this to happen the IAEA needs its inspectors in Iran. Tehran has postponed an important inspection visit until next month, saying it would conflict with national holidays.
But western diplomats say Iran has delayed inspections in the past in order to clean up and modify sites.
Further delays in the inspection process mean that the IAEA will not be able to make a full report to the next board of governors meeting, scheduled for June.