The UN atomic agency's board passed a resolution condemning Iran's nuclear activities after the watchdog's damning recent report but stopped short of setting Tehran a deadline to comply.
The text, proposed at the International Atomic Energy Agency by the five permanent members of the UN Security Council, Germany and 12 others, also drew the line at reporting Iran to New York.
Iran said it would not attend an IAEA forum next week on ridding the Middle East of nuclear weapons and that the resolution would only strengthen its resolve to press ahead with its "peaceful" nuclear programme.
The resolution said it was "essential for Iran and the Agency to intensify their dialogue" and calls on Tehran "to comply fully and without delay with its obligations under relevant resolutions of the UN Security Council."
A total of 32 countries on the 35-nation IAEA board of governors voted in favour, with Indonesia abstaining and Cuba and Ecuador voting against, diplomats said.
To assuage Chinese and Russian misgivings, the resolution has no timeframe for Iran to comply, calling instead for IAEA head Yukiya Amano to report to the board in March on Tehran's "implementation of this resolution."
Last week, the IAEA came the closest yet to accusing Iran outright of seeking to develop nuclear weapons, in a report immediately rejected by the Islamic republic as "baseless."
The US envoy to the IAEA, Glyn Davies, told the board on Friday that the "watershed report ... leaves little doubt that Iran, at the very least, wants to position itself for a nuclear weapons capacity."
He rejected criticism that the resolution was too weak.
"This resolution does the job," Davies told reporters. "It gives us the tools we need to get the job done."
"The United States will continue this pressure until Iran chooses to depart from its current path of international isolation, both in concert with our partners as well as unilaterally," a White House statement said.
Britain, France and Germany said in a joint statement they were "gravely concerned" by the report, saying it "paints a very disturbing picture ... The international community cannot simply return to business as usual."
But Iran's envoy Ali Asghar Soltanieh said it was "unprofessional, unbalanced, illegal and politicised" and has "deeply ruined the worldwide reputation of the Agency as a technical competent authority."
"Many parliamentarians ask me when they see me what the benefit is of being in the IAEA ... This is a legitimate question," he told reporters.
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"But the fact is Iran is in the IAEA to put the IAEA on the right track and prevent what the US wants to dictate to the IAEA. That is the reason I am here."
The report laid bare deep differences within the so-called P5+1 bloc dealing with the Iran question, the five permanent members of the UN Security Council -- the United States, China, Russia, Britain, France -- and Germany.
Washington, Paris and London jumped on the IAEA report as justification to increase pressure on Iran, already under four rounds of Security Council sanctions and additional US and European Union restrictions.
But Beijing, which relies heavily on Iranian oil imports, and Moscow, which also has close commercial ties and built Iran's only nuclear power plant, have been more cautious.
Israel's ambassador Ehud Azoulay on Thursday expressed disappointment at the resolution, having hoped for a stronger response and even what would be a fifth round of sanctions, saying the resolution "could be tougher."
But Western diplomats stressed all major powers had agreed, thus avoiding what would have been a potentially damaging split in the UN Security Council, where relations have already been tested this year over Libya and Syria.
"It is good we have a resolution supported by the six (powers)," a European envoy said. "It supports the work of the agency, condemns the lack of Iranian cooperation and calls on Iran to cooperate at last and without delay."
Mark Hibbs from the Carnegie Endowment for International Peace think tank said the text fails to single out weapons-related items in Amano's report, "and, most significantly, it doesn't set any deadline for Iran to comply."
After the IAEA resolution, UN leader Ban Ki-moon joined international demands for Iran to lift suspicions that it may be seeking a nuclear bomb.
"The secretary general remains deeply concerned about unresolved issues regarding the Iranian nuclear program, including those which need to be clarified to exclude possible military dimensions," said UN spokesman Martin Nesirky.
Ban called on Iran to cooperate "without delay" with the IAEA's proposal to send a high-level team to the Islamic republic.
"The secretary general emphasizes again that the onus is on Iran to prove the peaceful nature of its nuclear program," said Nesirky.
EU Foreign Policy Chief Catherine Ashton urged Iran to accept an offer of talks on its nuclear programme, saying in a statement the resolution was "a reaction to the particularly incriminating findings on Iranian military nuclear activities provided in the latest IAEA report."
German Foreign Minister Guido Westerwelle welcomed the resolution and threatened Tehran with new sanctions, saying: "If Iran continues to refuse serious negotiations on its nuclear programme, new sanctions will be inevitable.
"Iran has the choice between serious cooperation or international isolation," he added in a statement.
The Russian foreign ministry for its part played down the resolution, saying the document "does not aim at condemning anybody but at continuing dialogue and lowering tension."