The U.S. National Intelligence Estimate (NIE), published on Monday, stated that Tehran had put a stop to weapons production in 2003, although it was continuing to enrich uranium.
The report contradicted a previous U.S. intelligence assessment in 2005 which said that Iran was actively pursuing a nuclear bomb.
However, the U.S. envoy to the UN, Zalmay Khalilzad, said on Tuesday that he had received no new instructions from the Bush administration, and that he was preparing to complete work on a new sanctions resolution.
Commenting on the NIE at a news briefing, Khalilzad said, "Let me say what the NIE says and what it doesn't say. The NIE says that there was a covert military dedicated nuclear weapons program. That in 2003 stopped because of international pressure... But, it does not say that Iran does not have the intention to develop a nuclear weapons capability, that it has abandoned the goal of acquiring a nuclear weapons capability permanently."
The envoy's words echoed those of President George W. Bush, who said on Tuesday that, "Iran was dangerous, Iran is dangerous and Iran will be dangerous if they have the know-how to make a nuclear weapon."
When asked if military action remained an option, the president answered, "The best diplomacy - effective diplomacy - is one in which all options are on the table."
"What's to say they couldn't start another covert nuclear weapons program?" the president told a news conference at the White House.
International Atomic Energy Agency (IAEA) chief Mohamed ElBaradei welcomed the report, saying it was consistent with the agency's own findings and that it "should prompt Iran to work actively with the IAEA to clarify specific aspects of its past and present nuclear program."
"This would allow the agency to provide the required assurances regarding the nature of the program."
Russia, which has previously stated its opposition to increased sanctions against Teheran, did not comment on the NIE, although President Vladimir Putin insisted that Iran's nuclear program should be transparent and carried out under the supervision of the UN's nuclear watchdog, the IAEA. Iran's foreign minister was in Moscow on Tuesday for talks.
China has, however, demonstrated its opposition to new sanctions in more direct terms, saying that the UN Security Council would have to take into account the new information because "now things have changed".
Britain and France, who have backed U.S. calls for sanctions in the past, reiterated their commitment to maintaining pressure on Iran.
"We must maintain pressure on Iran," said French Foreign Ministry spokeswoman Pascale Andreani. "There is no new element that could make us change our position."
British Foreign Secretary David Miliband told BBC Radio that, "None of us want to see Iran as a nuclear proliferator. ... We have got to be clear there are negative consequences if they pursue enrichment which could lead to a nuclear weapons program."
Two sets of mild UN sanctions are already in place against Iran. China and Russia have both so far blocked the imposition of any new round of punitive measures against the Islamic Republic.