The U.N. atomic agency Wednesday censured Iran (search) for 18 years of secrecy, issuing a resolution that its director said gives him more muscle in policing the country for evidence of nuclear weapons ambitions.

Warning Tehran to stay in line, Director General Mohamed ElBaradei of the Vienna-based International Atomic Energy Agency (search) said the measure sends an "ominous message that failures in the future will not be tolerated."

"This is a good day for peace ... and nonproliferation," ElBaradei told reporters, saying the resolution, "strengthens my hand in ensuring that Iran's program is for peaceful purposes."

The resolution, adopted by consensus by the 35-nation IAEA board of governors, did not confront Iran with a direct threat of U.N. sanctions as the United States had initially sought. Key European powers opposed a direct threat, worried that Tehran would stop cooperating in retaliation.

The final resolution was a compromise, with a more implicit threat. It says that if "further serious Iranian failures" arise, the IAEA board would meet to consider actions allowed by its statute -- which include U.N. Security Council (search) action. If the IAEA turned to the council, the body would likely move to impose sanctions on Iran.

A senior U.S. official, who spoke to The Associated Press on condition of anonymity, said Washington was "pretty happy" with the compromise text. The source added that the U.S. is skeptical that Iran has stopped it covert nuclear weapons program.

Despite the lack of a direct threat in the resolution, White House spokeswoman Claire Buchan said that "there is no doubt ... further failures," by Iran would result in Security Council involvement.

While welcoming Iran's "offer of active cooperation and openness" -- including suspending uranium enrichment and agreeing to thorough inspections on IAEA demand -- the measure calls for a "particularly robust verification system" to test Tehran's honesty.

British Foreign Secretary Jack Straw said Wednesday the IAEA resolution was "an important step forward in the international community's efforts to prevent the proliferation of nuclear weapons." He added that he looks forward to "continued co-operation" with Iran.

Under intense international pressure, Tehran suspended enrichment recently and agreed to allow the implementation of stringent IAEA spot checks of its nuclear activities to demonstrate openness and cooperation with the agency.

The United States, which alleges that Iran plans to develop nuclear arms, had insisted last week it would hold out for at least a threat of Security Council action over 18 years of clandestine activities by Iran including uranium enrichment and plutonium processing.

But France, Germany and Britain opposed a direct Security Council threat, fearing Iran could backtrack on its cooperation were it too strongly pressured.

Backing the three European countries, Russian Foreign Minister Igor Ivanov speaking in Warsaw, Poland, agreed Wednesday, saying it "would have further complicated an uneasy situation."

In a slap at the United States and its allies, an Iranian statement said the resolution offered only "marginal relief to the few hard-liners" on the board.

"Iran's nuclear program is exclusively peaceful and will remain peaceful," said the statement.

ElBaradei said a new report on Iran will be ready in February, adding that the IAEA still has "a lot of work to do before we can conclude that Iran's program is exclusively for peaceful purposes."

U.S. envoy Kenneth Brill asserted that the resolution already found Iran in "noncompliance" -- and therefore pulled the "trigger" needed for Security Council involvement.

"The board will not countenance further evasive maneuvers by Iran," Brill told the meeting.

Later, he described Iran as being at a "crossroads."

"They can decide to continue down the well-worn path of the past -- almost 20 years of denial, deception and deceit -- or they can turn toward the path of a new chapter, wherein they really do come clean," he told reporters.

The United States, the European Union and most other members of the 35-nation board would like a permanent stop to Iranian uranium enrichment, but Iranian envoy Ali Akbar Salehi said that would not happen, describing the recent halt as temporary.