With Washington insisting that Iran is seeking nuclear weapons in violation of international agreements and in need of punishment, EU officials held fast to a softer line that criticizes Tehran but encourages dialogue.
In unusually blunt language, US Secretary of State Colin Powell derided the EU position as "just deficient" while his European colleagues defended their approach as logical and aimed at preventing confrontation.
At issue is a British, French and German draft resolution, prepared for submission to the UN's atomic watchdog this week, which faults Iran for failures in meeting certain obligations but does not explicitly find Tehran in "non-compliance" of them, as the United States demands.
"The resolution draft we saw earlier in the day was just deficient," Powell said en route here from Brussels to join US President George W. Bush's state visit to Britain.
"The resolution ... being presented by the 'EU three' was not adequate," he told reporters aboard his plane who accompanied him to the Belgian capital for meetings with European foreign ministers.
Specifically, Powell complained that the EU draft contained no "trigger mechanisms" setting performance benchmarks for the International Atomic Energy Agency (IAEA) to determine whether Iran is to avoid diplomatic or other sanctions.
A report from IAEA chief Mohammad ElBaradei released this month detailed a series of violations but said there was no evidence Iran is seeking to construct nuclear weapons, a conclusion Washington dismissed last week as "simply too impossible to believe."
Powell did not repeat that comment but seized on the other findings in ElBaradei's reports, saying: "The fact of the matter is that Iran has been in non-compliance."
Such a finding by the IAEA would send the matter to the UN Security Council for possible sanctions, a move that Iran, which vehemently denies the US charges, has said would trigger an international crisis.
Powell more generally lamented that the EU proposal was far too soft on Iran, which the United States has long accused of covertly developing nuclear weapons, and invoked the widely respected ElBaradei's name in doing so.
"I know that even Dr ElBaradei thought it was inadequate to the report he had prepared," he said.
Powell had discussed the proposed resolution on Tuesday in Brussels but made little headway in convincing his colleagues to adopt the US view.
"Dr ElBaradei is very clear that there has been behavior of Iran which is not compatible with what was expected," top EU diplomat Solana said at a joint news conference with Powell in Brussels.
But he stopped short of using the word "non-compliance," and pointed out that the British, French and German foreign ministers had secured an agreement last month from Tehran to halt uranium enrichment.
And, Solana noted that Iran had promised to sign an additional IAEA protocol allowing for spot inspections of its nuclear facilities.
Realizing these goals would go a long way in "preventing Iran from going nuclear" and forging a "good and constructive dialogue" on proliferation between Iran and the international community, he said.
Amid the stalemate, Powell said "intense discussions" on new language for the draft were underway at and between IAEA headquarters in Vienna as well as in Berlin, London, Paris and Washington.
"There is a lot of debate going on now," he said.
But diplomats in Vienna, as well as Powell and a senior State Department official, hinted that the two sides were so far apart that they might not be able to come to an agreement and the idea might be withdrawn.
The gap is so great that "there is no certainty there will be a resolution," when the IAEA board meets on Thursday.
A counter-resolution proposed by Australia on Tuesday strengthened the European text but still failed to cite Iran for non-compliance, diplomats said.
"We are now waiting for the Europeans to give us changes in their text," said one. "The Americans seem to have their own views," he said.
The majority of IAEA states, including non-aligned and Latin American countries, think like Britain, France and Germany that Iran should not face possible UN sanctions but be encouraged to cooperate, diplomats said.
Powell rejected that view as unrealistic.
"We're pleased that Iran seems to be responding to international pressure ... but this is not something that we should be congratulating them about," he said on his plane.