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The U.N. atomic watchdog agency censured Iran for past cover-ups in its nuclear program in a resolution adopted Friday, warning Tehran to be more forthcoming.

While escaping sanctions, Iran threatened that it still might retaliate by reconsidering plans to suspend its uranium enrichment.

In harsh language, the resolution approved by the 35-member board of governors of the International Atomic Energy Agency (search) said it "deplores" that "Iran's cooperation has not been as full, timely and proactive as it should have been."

It notes that since Iran's undeclared program came to light two years ago, "a number of questions remain outstanding."

The resolution submitted by France, Germany and Britain was a product of days of diplomatic maneuvering over the wording.

IAEA Director General Mohamed ElBaradei (search) said the resolution "calls in very explicit terms on Iran to accelerate its cooperation with the agency."

Asked whether a deadline was needed to force Tehran to comply, he said the board "expects these issues to come to a close in the next few months."

U.S. Undersecretary of State John R. Bolton said Washington was "very pleased."

"The results will keep Iran's nuclear program and its efforts to deceive and obstruct IAEA inspectors at the center of international attention for quite some time," he said in a statement to The Associated Press.

In a veiled condemnation of the United States, which insists Tehran has nuclear weapons ambitions, Iranian delegate Amir Zamaninia told the meeting that the tone of the resolution was affected by "wild and illusionary allegations of a secret Iranian nuclear weapons program."

He warned that his country was reviewing its "voluntary confidence-building measures," an indication that Iran might rethink the suspension of its uranium enrichment activities. Enrichment can lead to fuel for electricity or weapons-grade uranium for warheads.

As the agency put final touches on the wording late Thursday, diplomats speaking on condition of anonymity said the IAEA was looking into accusations that Iran was razing parts of a restricted area next to a military complex in a Tehran suburb. Satellite photos showed that several buildings had been destroyed and topsoil had been removed at Lavizan Shiyan, one diplomat said.

Iran's chief delegate to the IAEA's board of governors, Hossein Mousavian, denied there was a cover-up and told the AP the agency was free to see the site. "There is nothing there," he said.

Asked about Lavizan Shiyan, ElBaradei said his agency would "like to ... clarify" suspicions about the site, but he added that the IAEA for now was withholding judgment on whether there had been undeclared nuclear activities there. He said he hoped inspectors could go to the site and report their findings to the next scheduled board meeting in September.

Chief U.S. delegate Kenneth Brill, in comments to the board Friday, accused Iran of taking "the wrecking ball and bulldozer" to the site "to deal with some particularly incriminating facts."

He said the resolution put the board "on record as rejecting Iran's continuing tactics of delay, denial and deception."

Most of the still-unanswered questions in Iran focus on the sources of traces of highly enriched uranium found at several sites in Iran, and the extent and nature of work on the advanced P-2 centrifuge, used to enrich uranium.

Though the resolution does not give a deadline, it states that it is essential for Iran to deal with issues "within the next few months."

It does not contain a "trigger mechanism" — a clause sought by Washington that could send the Iran case to the U.N. Security Council for violating the Nuclear Nonproliferation Treaty.

Tehran says the minute finds of highly enriched uranium were not produced domestically but were inadvertently imported in purchases through the nuclear black market — an assertion the agency has not yet proven.

Tehran says it is interested only in generating electricity; Washington says Iran's nuclear activities are a smoke screen for a weapons program.

In a clear warning to Iran that its activities will be closely followed, the resolution also asked ElBaradei to report on his findings "well in advance" of the next board meeting in September if warranted.

The rebuke was agreed on despite Iranian efforts to tone it down substantially, including tactics that led ElBaradei on Thursday to acknowledge one mistake in a report criticizing Tehran for repeated lack of cooperation with the agency probe.

Earlier, the agency criticized Iran for not admitting to a purchase of 150 magnets for P-2 centrifuges that Iran was building secretly. On Thursday, ElBaradei acknowledged the veracity of an audio tape submitted the day before by Iran that records an agency inspector being informed about their purchase.

The report also said Iran inquired about buying thousands of such magnets on the black market — substantially more than Tehran needed for what it said was a research program. ElBaradei on Thursday said Iran expressed interest in 100,000 of such magnets.

"We still have no concrete proof that this has a military dimension but we are still are not in a position to say that this is exclusively for peaceful purposes," ElBaradei said.

Iran asserted the revelation showed its honesty.