GENEVA -- As negotiations get under way in Geneva Tuesday on Iran's disputed nuclear program, expectations are running higher than they have in a decade. But the barriers that remain are daunting, and are likely to center on what the experts call Iran's "breakout capacity," the ability to build a nuclear weapon in a matter of months, and its willingness to accept intrusive inspections.
Iran is expected to propose a moratorium on enrichment to 20 percent, a level that experts say is worrying, while restricting enrichment to the range of 3 percent to 5 percent that is used in commercial reactors. In return, it wants quick reciprocal gestures from the United States, a step that a senior American official said the Obama administration was prepared to take.
"We are quite ready to move," said the official, who added that the American delegation to the talks, scheduled to start on Tuesday, includes top experts on the economic sanctions that have heavily damaged on Iran's economy.
But the senior official also said that the United States and its partners in the talks would first wait to see if Iran was prepared to take concrete steps to constrain the pace and scope of its nuclear program, address its growing stockpile of enriched uranium and provide a new degree of transparency about its nuclear activities.
"We are going to make judgments based on the actions of the Iranians," said the senior official, who spoke on condition of anonymity in keeping with diplomatic protocol.
The talks in Geneva are the first between Iran and the big powers since the election of a new Iranian president, Hassan Rouhani, who took office in August and has made a priority of easing the crippling sanctions on Iran over its nuclear activities. The rounds of talks under Mr. Rouhani's predecessor, Mahmoud Ahmadinejad, made no progress.
The new Iranian president's foreign minister, Mohammad Javad Zarif, has announced that he intends to present a new proposal when the talks open here on Tuesday to persuade world powers that the country's nuclear program has only peaceful aims, a top official said on Sunday.
The P5-plus-1 talks with Iran, as they are known in diplomatic shorthand, involve the five permanent members of the United Nations Security Council -- Britain, China, France, Russia and the United States -- plus Germany.
The United States had asked Iran to present the proposal before the Tuesday meeting so the Obama administration and its foreign partners would be in a better position to respond.
Iran's reluctance to do so, as well as uncertainty on whether it was prepared to make far-reaching concessions, has led to some caution on the Western side. Secretary of State John Kerry and his counterparts from Western nations are not planning to attend.
In comments on Sunday, Abbas Araghchi, Iran's deputy foreign minister, said that the proposal would involve a three-step plan that would establish the independence of Iran's civilian nuclear program while providing assurances that the country is not trying to produce nuclear weapons.
"We need to move towards a trust-building road map with the Westerners," Mr. Araghchi told the Iranian Students' News Agency in an interview. "To them, trust-building means taking some steps in the nuclear case, and for us this happens when sanctions are lifted."
Iranian officials have not publicly described the details in public. But there has been speculation that a major element will be a commitment to stop the production of uranium that is enriched to 20 percent purity, which is a short technical step away from highly enriched uranium required for bomb-grade fuel. Fuel needed for civilian reactors, by contrast, is low-enriched uranium of 5 percent or less.
American experts said that if a moratorium on 20 percent enriched uranium turns out to be the centerpiece of the new Iranian proposal it will fall short of what is needed to stop Iran from developing a "breakout" capability -- the capacity to rapidly develop a nuclear weapon.
"Ending production of 20 percent enriched uranium is not sufficient to prevent breakout because Iran can produce nuclear weapons using low-enriched uranium and a large number of centrifuge machines," said Gary Samore, a former proliferation expert on the Obama's administration's National Security Council, who is now the president of United Against Nuclear Iran, a group that strongly advocates tough sanctions.
"The U.S. is looking for an agreement that limits Iran's overall enrichment capacity, defined in terms of numbers and types of centrifuges and stockpile of low enriched uranium, in exchange for substantial sanctions relief," Mr. Samore added.
The Obama administration has never said publicly whether it might be prepared to accept an Iranian right to enrich uranium to low levels as part of any agreement.
Thomas Erdbrink contributed reporting from Tehran.world
This article originally appeared in The New York Times. First Published October 14, 2013 2:01 PM