The United Nations nuclear agency is accusing Iran of blocking a U.N. investigation into allegations that Tehran tried to make nuclear weapons.
The International Atomic Energy Agency made the accusation in a restricted report released by U.N. officials to the media on Monday.
In the report, the IAEA says it has made no substantive progress in its investigation of alleged Iranian nuclear weapons studies. The agency says it remains seriously concerned about the programs.
U.N. officials say the accusations are backed by detailed evidence and must be taken "seriously" by Iran.
The IAEA report also says Iran continues to enrich uranium in defiance of U.N. Security Council resolutions. U.N. officials say Iran has amassed one-third of the enriched uranium it would need to make a nuclear weapon and could obtain the rest within two years.
Iran says its nuclear program is peaceful. It says allegations of nuclear weapons research are forged.
The IAEA's 35-nation board is due to discuss the report next week.
The White House responded to the report by saying Iran's actions are further isolating its people from the international community. U.S. officials say Iran risks new international sanctions if it continues to defy the U.N.
German Foreign Minister Frank-Walter Steinmeier discussed the Iranian nuclear dispute Monday with his Iranian counterpart, Manouchehr Mottaki, in Berlin.
German officials say Steinmeier expressed disappointment with what he viewed as Iran's lack of cooperation with the IAEA. Steinmeier is quoted as saying that Iran should stop playing for time and give the U.N. agency the information it needs.
Washington and its allies have accused Iran of trying to develop nuclear weapons under cover of a civilian energy program, a charge Tehran denies.
Some information for this report was provided by AFP, AP and Reuters.