Iran's resumption of sensitive nuclear activities may represent a defiant challenge to the West's entire nonproliferation strategy for Tehran.
That's because the Iranian move to restart its Isfahan uranium-conversion plant is something European negotiators directly asked the government not to do.
In technical terms, Iran today is no closer to obtaining nuclear weapons. Conversion is a process that precedes enrichment - the refining of uranium to bomb-ready grade.
But in flouting Germany, France, and Britain - the three nations that have taken the lead in the negotiations - Iran has essentially dared the United States and its European allies to start some kind of punishment process. The negotiations themselves, involving as they do a mixture of carrot inducements and implied use of sticks, might now be in trouble.
"What is worrisome is this creates the very real possibility that the two-year diplomatic process aimed at resolving this crisis is in severe jeopardy," says Daryl Kimball, executive director of the Arms Control Association.
It's possible that Iran might yet reverse its sudden spurt of North Korean-style brinkmanship. New Iranian president Mahmoud Ahmadinejad has said he is eager for more talks and will propose new approaches soon.
But on Wednesday Iran broke International Atomic Energy Agency (IAEA) seals at the Isfahan plant, paving the way for the full reopening of the facility. IAEA officials themselves removed the seals, per Tehran's request, after installing surveillance cameras to try to ensure no uranium is diverted to clandestine uses.
Under the terms of the Nuclear Non-Proliferation Treaty (NPT), of which Iran is a signatory, processing and enrichment of uranium for peaceful purposes are allowed. Iran thus isn't breaking the treaty with resumption of nuclear fuel work.
But Iran had agreed to a halt last November, after the IAEA found that Tehran had hidden weapons-grade fissile material. Germany, France, and Britain - referred to as the EU3, for the purposes of negotiations with Iran - argue that the only way Tehran can prove it has no intention of obtaining weapons is now to renounce nuclear fuel cycle activity, even though it would be allowed under the NPT.
"The door remains open for Iran to come back to the [negotiation] process by urgently halting all work," said a British Foreign Office statement released on Wednesday.
For now, the next steps of the EU3 and the US remain unclear. The IAEA board of governors postponed an emergency meeting originally scheduled for Wednesday so that diplomats could confer privately on the matter.
Other developing nations on the IAEA board may not be eager to agree to refer Iran to the United Nations Security Council for consideration of sanctions.
Diplomats "need more time" to develop a consensus approach, said IAEA spokesman Peter Rickwood.
The lack of quick IAEA board consensus is not something to worry about, says Mr. Kimball of the Arms Control Association.
What's more important, he says, is what eventually emerges from the huddle.
"I think it is important for the credibility of the EU3 and other board members that they issue a very strong reprimand," he says.
It's possible that by showing a touch of belligerence Iran is in fact playing into the hands of US officials who favor a tougher approach to negotiations with Tehran.
The US has demonstrated patience by allowing the Europeans to take the lead in dealing with Tehran, in this analysis. Having tried to woo Iran with offers of economic assistance, as well as ready-made fuel for nuclear-power plants, the West may now be in a better position to press for Security Council action.
The Iranians "may have miscalculated and may be playing into the hands of those elements in the Bush administration who would like to see Iran behave in the most belligerent fashion possible in order to fashion the toughest possible response," Kimball says.
What US officials need to do now is push the Europeans behind the scenes to show resolve on the issue, say other experts.
Iran may be betting that its actions will reexpose a split between Europe and its harder-line US partner.
"One advantage of this scenario is it gives the Europeans an opportunity to demonstrate that there is more agreement on this across the Atlantic than the Iranians think," says Lee Feinstein, deputy director of studies at the Council on Foreign Relations.
Iran may also be sending a message to the rest of the world: Its cessation of nuclear fuel work was a temporary gesture of good will, not a permanent condition.
The Iranians could well have used the halt at the Isfahan plant to work out acknowledged technical problems.
"For political and technical reasons they may now be eager to proceed," says Charles Ferguson, an expert on nuclear technology and proliferation at the Council on Foreign Relations.
There might be a compromise outcome to the current standoff, says Mr. Ferguson.
The West could agree to allow Iran to proceed with a small amount of nuclear research, up to and even including enrichment of nuclear fuel, says Ferguson. In return, Tehran could perhaps allow the IAEA to intensely monitor the work and try out enhanced safeguard and verification methods.
"Iran could serve as a leading example to the rest of the world, and that way we would not be denying them any sovereign right to engage in these activities," says Ferguson.