This abrupt switch follows the failure of Iran's strategy, adopted last October, of coming clean on part of its nuclear activities, while trying to keep the rest walled off. The Feb. 24 report by the IAEA Director-General exposed this failure to the international community, changing the dynamics of the situation.

In other words, the Iranians figured that they could fool the inspectors until the process petered out, but they underestimated their resourcefulness and determination.

(See my analysis of what the Feb. 24 report reveals about uranium in Iran.)

America's strategy increasingly seems based on the recognition that Iran cannot be stopped from getting the bomb, but it can and must be made to pay a price if it chooses to do so. By Wednesday, while the exact language of the IAEA resolution was being negotiated, a U.S. official already was gloating anonymously that the Iranians could no longer get the bomb without risking a harsh price:

American officials are lobbying hard to keep international pressure on Iran.

An I.A.E.A. resolution on Libya, passed by the agency's board of governors on Wednesday, is part of that campaign. The resolution, negotiated by the United States, Britain and Libya in London last week, praises Libya for swiftly dismantling the nuclear weapons program discovered last year. But the resolution's key paragraph calls for the agency to report Libya's past breaches of the Nonproliferation Treaty to the United Nations Security Council.

"The trap is sprung," said a senior American administration official speaking from Washington, saying that the Libyan resolution sets a precedent for future I.A.E.A. resolutions on Iran. "It makes it very hard not to at some point address Iran's breaches by referring them to the Security Council," he said.

(The IAEA resolution on Libya is here.)

On Friday, the day before the IAEA Board of Directors met to vote on the draft resolution, Pirooz Hosseini, Iran's Vienna-based ambassador to the IAEA, announced that Iran had decided to delay the inspectors' upcoming visit until late April, citing the No Ruz spring equinox holiday. This move was understood at the time as a shot over the bow -- a threat not to make the resolution too tough. But in hindsight, it looks like a sign of panic.

On Saturday, after a week's debate over wording, the IAEA Board of Governors passed its resolution on Iran. The text, running slightly over two pages long, briskly catalogues Iran's most significant failures to live up to its October pledge and calls on Iran "to be pro-active in taking all necessary steps on an urgent basis to resolve all outstanding issues" -- that is, to come clean for real. It asks the IAEA Director-General to file a follow-up report before the end of May, in time for the Board's June meeting. Only then will the board consider "how to respond to the above-mentioned omissions."

Iran's response, tonight, was to declare the inspections process frozen.

"Today, I.A.E.A. inspectors were expected to arrive in Iran," Iran's top nuclear negotiator, Hassan Rowhani, said at a news conference in Iran's capital, Tehran. "We will not allow them to come until Iran sets a new date for their visit. This is a protest by Iran in reaction to the passage of the resolution."

As a former U.S. nonproliferation official recently explained it,

The administration has to confront Iran with a united front and force it to make a choice between being a pariah state with nuclear weapons or being a member of the international community without nuclear weapons.

Analyst

The IAEA's Iran page is here. My previous assessments of Iran's nuclear program are here, here, and here. Earlier, Ami Isseroff asked whether Iran really needs nuclear power.

My earlier comments on Libya's nuclear program are here and here.