WASHINGTON - As diplomats began drafting a comprehensive agreement on the Iranian nuclear programme and Western sanctions in Vienna Tuesday, U.S. officials were poised to demand a drastic cut in Iran's enrichment capabilities that is widely expected to deadlock the negotiations.
Iran is almost certain to reject the basic concept that it should reduce the number of its centrifuges to a fraction of its present total, and the resulting collapse of the talks could lead to a much higher level of tensions between the United States and Iran.
The Obama administration's highly risky diplomatic gambit rests on the concept of "breakout time", defined as the number of months it would take Iran to accumulate enough weapons grade uranium for a single nuclear weapon.
The Barack Obama administration's highly risky diplomatic gambit rests on the concept of "breakout time", defined as the number of months it would take Iran to accumulate enough weapons grade uranium for a single nuclear weapon.
Both Secretary of State John Kerry and former U.S. proliferation official Robert Einhorn have explained the demand that Iran give up the vast majority of its centrifuges as necessary to increase Iran's "breakout time" to at least six months, and perhaps even much longer.
Einhorn, the State Department's special adviser for nonproliferation and arms control until June 2013, wrote in a report for the Brookings Institution that the number and type of centrifuges "will be limited to ensure that breakout times are...a minimum of 6 to 12 months at all times."
In a separate article in The National Interest, Einhorn wrote that such a "breakout time" would entail a reduction from Iran's present total of 19,000 centrifuges to "a few thousand first-generation centrifuges".
Kerry suggested in testimony before the Senate Foreign Relations Committee Apr. 8 that the administration would try to get a breakout time of more than one year but might settle for six to 12 months. He compared that with the two months he said was the current estimate of Iran's breakout capabilities.
"Breakout" has been touted by hardline think tanks as a non-political technical measure of the threat to obtain the high-enriched uranium necessary for a bomb, but it is actually arbitrary and highly political.
Even proliferation specialists who support the demand to limit Iranian enrichment capabilities severely, however, including both Einhorn and Gary Samore, Obama's former special assistant on weapons of mass destruction, believe that "breakout" is more about the politics surrounding the issue than the reality of the Iranian nuclear programme.
In an interview with IPS, Samore said the breakout concept can only measure the capability to obtain the necessary amount of high-enriched uranium from acknowledged facilities - those that are under inspection by the International Atomic Energy Agency (IAEA).
It does not deal with a scenario involving secret facilities, he said, because it is only possible to estimate rates of enrichment in facilities with known quantities and types of centrifuges.
The use of the breakout concept is based on the premise that Iran would make a political decision to begin enriching uranium to weapons grade levels in its Natanz and Fordow plants as rapidly as possible. That would mean that Iran would have to expel the IAEA inspectors and announce to the world, in effect, its intention to obtain a nuclear weapon.
Samore, who left the Obama administration in January 2013 and is now the executive director for research at Harvard's Belfer Center for Science and International Security, told IPS, "It's extremely unlikely that Iran would actually take the risk for single bomb," calling it "an implausible scenario."
Samore is no dove on Iran's nuclear issue. He is also president of United Against Nuclear Iran, an organisation that puts out hardline propaganda aimed at convincing the world that Iran is a threat trying to get nuclear weapons.
Another problem with the spectre of "breakout" is that, even if it took the risk of enriching the necessary weapons-grade uranium, Iran would still have to go through a series of steps to actually have a bomb that it could threaten to use.
A report released last week by the International Crisis Group (ICG) noted that calculations of breakout capability "are rough and purely theoretical estimates" and that they "omit inevitable technical hitches" and "an unpredictable and time-consuming weaponisation process."
According to the testimony by director of the Defence Intelligence Agency. Lt. Gen. Ronald Burgess before the Senate Armed Services Committee in April 2010, that process, including integrating the weapon into a ballistic missile, would take three or four years.
The ICG report quoted a senior Iranian official as saying, "Serious people know that, even if Iran sought nuclear weapons, it will take years to manufacture one. What's more, no state has ever invited opprobrium or a military strike just to produce a few kilograms of highly enriched uranium."
In an interview, Jim Walsh of MIT's Security Studies Programme was scathing about the "breakout" scenario the administration is using to justify its diplomatic stance. "The idea of Iran kicking out inspectors to rush to get one bomb is silly," he told IPS.
Samore believed that Iran would be far more likely to try what he calls a "sneakout" - the use of secret facilities to enrich uranium to weapons grade -- than a "breakout".
But as is generally acknowledged by proliferation specialists, such a covert route to a nuclear weapons capability would take much longer than trying to do so openly. Furthermore, it is almost certain to be detected, as Director of National Intelligence James Clapper testified in April 2013.
Despite his conviction that the breakout concept makes no sense as the basis for negotiations with Iran, Samore believes it will be "the test for any deal", because it is the only way to measure it. "It's a political fact of life," Samore said. "It all gets boiled down to breakout time."
The dominance that the breakout advocates have achieved in the lopsided Iran political discourse has given opponents of an agreement a new form of pressure on the Obama administration to make unrealistic demands in the negotiations.
Einhorn admitted at a panel at the U.S. Institute of Peace in Washington D.C. Tuesday that the decision on the length of breakout time and the level of centrifuges to be demanded "will come down to a political judgment".
He clearly suggested, however, that the decision is primarily a response to political pressures from various unnamed parties and not a matter of finding a political compromise with Iran.
"Some say six months or less," he said. "Others say you need a year. Some say a year and a half or two years."
The former senior State Department official on proliferation issues insisted, moreover, that there was no possibility of accepting Iran's explicit demand to be permitted to increase its enrichment capacity to as many as 30,000 centrifuges in order to support a nuclear power programme.
"That amount would bring breakout time down to weeks or days," he said. "That's breakout."
He did not discuss the possibility of agreement on gradually phasing in additional centrifuges as the practical need for them is demonstrated by progress on a new nuclear reactor.
The tough talk by Einhorn, who has clearly been given the green light to describe administration thinking publicly, makes it much less likely that the administration will back away from a breakout demand in the face of firm Iranian resistance.
Gareth Porter, an investigative historian and journalist specialising in U.S. national security policy, received the UK-based Gellhorn Prize for journalism for 2011 for articles on the U.S. war in Afghanistan. His new book "Manufactured Crisis: the Untold Story of the Iran Nuclear Scare", was published Feb. 14.