The United States said Wednesday that the latest findings by the United Nations' nuclear watchdog agency make clear that close scrutiny of Iran's nuclear program should continue. U.S. officials have long believed that despite denials, Iran is trying to conceal a nuclear weapons program.

The United States is dismissing Iran's suggestion that the International Atomic Energy's case against it is nearly closed. It says Iranian nuclear activity should remain under close watch "for the foreseeable future."

The comments, from the State Department, follow the release at the IAEA in Vienna Tuesday of a report by the U.N. agency's director-general, Mohammed ElBaradei, which says that important issues about Iran's nuclear program remain unresolved.

The IAEA report, circulated in advance of a meeting this month of its 35-nation governing board, credits Iran with providing new information about its nuclear efforts. But it also cites a wide array of missing details and contradictory explanations of its activities, including acquisition of uranium-enriching centrifuges.

Iranian officials, who say their nuclear program is entirely peaceful, said the report shows that only minor questions remain and that the IAEA probe should be nearing an end.

But briefing reporters, State Department spokesman Richard Boucher said the new information shows that Iran is continuing to try to conceal relevant material and delay inspections, in line with what he said has been 18 years of documented clandestine nuclear activity.

"Tehran has repeatedly failed to declare significant and troubling aspects of its nuclear program," he said. "It has interfered with and suspended inspections. It has failed to cooperate with the International Atomic Energy in resolving outstanding issues relating to its nuclear program. It is clear that the International Atomic Energy Agency's investigation and verification work in Iran must continue for the foreseeable future."

Mr. Boucher, who called on Iran to "make good" on repeated promises of full cooperation with the IAEA , said there is no doubt that many aspects of its nuclear program "are in no way peaceful."

But under questioning, he declined to say if the United States would press at the board meeting, which begins June 14, to have the matter referred to the U.N. Security Council for possible sanctions against Iran.

He said U.S. officials look forward to that discussion, but that it will be up to the IAEA governors to decide what to do.