Under fire for stalling a 130-nation nuclear meeting, Iran on Friday accused the US of being the real culprit, as the conference adjourned for the weekend in deep deadlock over Teheran's opposition to language of the gathering's agenda.
With the dispute in its fifth day, several non-Iranian diplomats at the conference said it could be dissolved without progress by Monday unless differences were resolved.
At issue is Teheran's refusal to accept a phrase calling for the "need for full compliance with" the Nuclear Nonproliferation Treaty.
That position has delayed adoption of the agenda since the conference opened Monday. Teheran argues the language could lead it to become a target at the meeting because of its refusal to heed UN Security Council demands to cease uranium enrichment and other parts of its nuclear program that could be misused to make nuclear weapons.
"If I reduce it to a simple sentence, it's this: The Iranians are blocking things," said a senior European diplomat.
But Iran's chief delegate to the meeting said Washington was to blame, accusing it of manipulating the meeting's chairman to work against Teheran.
"I'm sure the United States is hiding behind and pushing him," said Ali Ashgar Soltanieh, referring to conference chairman Yukiya Amano of Japan, in comments to reporters outside the meeting.
In a move to placate Iran, Amano - who drew up the agenda - told the meeting his intention was to make clear in the text that "compliance with the treaty is compliance with all provisions of the treaty" - an allusion to commitments by nuclear weapons states to disarm.
Soltanieh, however, insisted that the agenda language itself be changed to include the "all provisions" phrase - something Amano refused to do, in a decision publicly backed by the European Union, Canada and Australia but opposed by Syria and Venezuela.
The harsh tone of debate reflected tempers frayed by the lack of progress at the meeting since it opened Monday. The two-week conference is meant to review and tighten the treaty.
Iran has said it is determined to expand its disputed nuclear program and further defy UN demands that it freeze all preparations for enrichment, a potential pathway to nuclear arms.
Before Friday's abortive sessions, diplomats familiar with Iran's nuclear program said Teheran had recently set up more centrifuges at its underground uranium enrichment plant at Natanz, bringing the number of machines ready to spin uranium gas into enriched form to more than 1,600.
The diplomats spoke on condition of anonymity because they were not authorized to comment on internal conference matters to the media.
An International Atomic Energy Agency document obtained last month said the Islamic regime was running more than 1,300 centrifuge machines to enrich uranium at its Natanz facility.
Its ultimate goal is to have 50,000 centrifuges. That would be enough to supply fuel for what Teheran says is a planned network of atomic reactors to generate electricity - or material for a full-scale nuclear weapons program.
The expansion of Iran's enrichment program is also linked to the main issue of contention at the Vienna conference.
Amato adjourned the meeting after Iran asked for time to decide on its response to a South African suggestion meant to end the deadlock. The proposal would have delegates - who normally work on consensus - decide on whether an appended statement to the agenda stating that "all aspects" of compliance to the treaty were needed.
But even before that, pessimism grew about what the meeting could accomplish before its scheduled end on May 11.