Iran's nuke program _ how much time for diplomacy?

ISTANBUL – The U.S. is joining five other world powers for talks with Iran this week publicly confident that international efforts have slowed Tehran's capacity to make nuclear arms and created more time to press Tehran to accept curbs on its atomic activities.

But the Federation of American Scientists is warning against complacency. It says there have been impressive improvements in the performance of the Iranian machines that enrich uranium — an activity that has provoked U.N. sanctions because it could be used to make nuclear weapons.

In a study shared with The Associated Press ahead of publication, the Washington-based organization argues that Iran last year appears to have increased efficiency of the machines that produce enriched uranium by 60 percent, giving it the technical capacity to produce enough material for a simple nuclear warhead in 5 months.

Still, Washington has joined diplomats and officials at the International Atomic Energy Agency — the U.N. monitor of Iran's nuclear program — in saying the nation is struggling with uranium enrichment, a process that can create both nuclear fuel and fissile warhead material.

And Israel, Iran's implacable foe and considered to have the Mideast's best intelligence on Iran's nuclear strivings, has agreed.

So Washington's message is essentially this: There is more time to negotiate with Iran in the hope that it will come around and give up enrichment — thereby removing the threat of an Israeli or U.S. military strike on Iran's nuclear facilities.

Iran insists it is enriching only to make nuclear fuel, and Ivanka Barzashka, author of the Federation of American Scientists study, emphasizes that Tehran is unlikely to provoke the world — and increase the likelihood of attack — by kicking out IAEA inspectors and re-calibrating its centrifuges from making low-enriched to weapons grade uranium.

Olli Heinonen, who retired late last year as the IAEA deputy director general in charge of the agency's Iran file, called the likelihood of such a "breakout scenario" as a "suicidal mission" and noted that manufacturing nuclear warhead material is only one step in making a weapon. But he also said he cannot "dispute the correctness of the figures" in the study.

The two sides are coming to the table at Istanbul for Friday's talks as far apart as they were at the end of their first round in Geneva last month. Barzashka said that efforts to bridge the divide must be increased.

"The biggest issue with recent statements that Iran's nuclear drive has been slowed down is that we are getting a false sense of security that we have bought more time," Barzashka said in an e-mail. "That takes away from the urgency ... (of) a diplomatic breakthrough."

Barzashka based her conclusions on data of nuclear material fed into enriching centrifuges and the output of these machines collected by the International Atomic Energy Agency.

An IAEA official who read Barzashka's 14-page study called her conclusion of impressive progress in output of enriched uranium "very solid" and "based on the best possible data."

But that official and a senior diplomat based in Vienna familiar with Iran's enrichment efforts said overall the centrifuges continued to perform substantially below capacity. Both spoke on condition of anonymity because they were not authorized to comment to the media.

The Federation of American Scientists study says the increased output by thousands of centrifuges at Iran's centrally located underground facility at Natanz could either be due to better recovery of previously wasted feedstock or increased efficiency of the centrifuges that spin gas into enriched uranium.

"Contrary to statements by U.S. officials and many experts, Iran does not appear to be slowing down its nuclear drive," it says.

Such views contrast with the public optimism expressed by Washington ahead of the Istanbul talks convened by the European Union, with Iran on one side of the table and the U.S. Russia, China, Britain, France and Germany on the other.

Israeli officials now talk of a three-year window — until 2014 — before Iran can make a bomb. That compares with projections of 2011 just three years ago.

U.S. Secretary of State Hillary Clinton told NBC's "Today" show on Wednesday that the new Israeli estimates are "very significant." The delay, she said, "gives us more of a breathing space to try to work to prevent them from obtaining a nuclear weapon."

Two outside forces could account for any Iranian problems in enriching uranium — the increasing weight of U.N. sanctions, meant to choke off raw materials needed to make and maintain the program, and the apparent havoc caused by the mysterious Stuxnet computer malware.

Iran has acknowledged that Stuxnet hit "a limited number of centrifuges," saying its scientists discovered and neutralized the malware before it could cause any serious damage. The computer worm is assumed to have caused disruption of enrichment in November that temporarily crippled thousands of centrifuges at Natanz.

Barzashka said that while the sanctions might have slowed Iran's ability to develop, new and more efficient centrifuges, they do not seem to have slowed improvements in the output of the present generation of machines used at Natanz.

Ahead of the talks, Iran is trying to take the diplomatic offensive.

It is pushing an agenda that covers just about everything except its nuclear program: global disarmament, Israel's suspected nuclear arsenal, and Tehran's concerns about U.S. military bases in Iraq and elsewhere in the region.

"We want to discuss the fundamental problems of global politics at Istanbul talks," said Iranian chief negotiator Saeed Jalili before arriving in Istanbul on Thursday.

President Mahmoud Ahmadinejad suggested any push to restrict the meeting to Iran's nuclear program would fail.

"They employed all their might and tried hard to prevent Iran from going nuclear," Iranian state TV quoted him as saying. "But Iran went nuclear and there will be no way back."

Foreign Minister Sergey Lavrov of Russia — which Iran has depended on to blunt past U.N. penalties — suggested there was room for non-nuclear themes, saying "legitimate Iranian concerns" also could be discussed.

But Lavrov also said Iran should to agree to intrusive inspection of its nuclear sites. "It's not an obligation, but it will certainly be required, given the history of the Iranian nuclear issue," he said.

The U.S. and others fear Iran's enrichment program could eventually lead to nuclear weapons. Iranian officials say they only want reactors for energy and research — and that the Nuclear Nonproliferation Treaty gives Iran the legal right to enrich uranium and produce nuclear fuel.

"We seek to launch a meaningful and practical process that addresses the core issues with Iran's nuclear program," U.S. State Department spokesman Philip J. Crowley said on the eve of the talks. The six powers, he said, "are committed to holding Iran accountable to its international obligations, and will continue to do so until Iran takes tangible steps to resolve international concerns with its nuclear program."

Uranium enrichment lies at the heart of the dispute.

Low-enriched uranium — at around 3.5 percent — can be used to fuel a reactor to generate electricity, which Iran says is the intention of its program. But if uranium is further enriched to around 90 percent purity, it can be used to develop a nuclear warhead.

Iran's ambassador to the U.N.'s International Atomic Energy Agency, Ali Asghar Soltanieh, said the Istanbul talks are a "window for an honorable path for the West to get out of the present impasse."

But Christopher Hill, a former U.S. assistant secretary of state for East Asia, said sanctions should be a tool of diplomacy.

"Just as the U.S. adopted a 'bomb and talk' approach with the Serbs during the denouement of the Bosnian war, America must be willing to 'sanction and talk' when it comes to Iran, thereby creating greater space for an eventual diplomatic strategy," Hill said.

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Jahn reported from Vienna. Associated Press writers Edith M. Lederer at the United Nations, Matthew Lee in Washington and Vladimir Isachenkov in Moscow contributed to this report.