PARIS — Tensions between the West and Russia over events in Ukraine have cast a shadow over the second round of talks set to begin on Tuesday in Vienna on a permanent nuclear agreement with Iran.
Although the talks have no direct connection to Ukraine, their success hinges on solidarity among the so-called P5-plus-one countries — the five permanent members of the United Nations Security Council, which include Russia, plus Germany — in favor of a tough agreement with Iran to drastically scale back its nuclear program.
If Russia signals that its cooperation with the West has weakened, that will reduce pressure on Iran to make concessions, said experts knowledgeable about the talks, which began last month with three days of meetings involving senior diplomats from each of the governments involved.
A senior American official, speaking before the Iran talks and just before the secession vote in Crimea on Sunday that overwhelmingly approved reunification with Russia, indicated concern about possible consequences from the friction over Ukraine. Since western nations consider that vote illegal and have warned President Vladimir V. Putin of Russia not to annex Crimea, the situation for the Iran talks would now seem more worrisome.
“I think that we all hope that the incredibly difficult situation in Ukraine will not create issues for this negotiation,” said the official, speaking on the condition of anonymity because of the sensitivity of the talks.
“We hope that whatever happens in the days ahead, whatever actions we and the international community take, depending upon the decisions and the choices that Russia makes, that any actions that Russia subsequently takes will not put these negotiations at risk,” the official said.
Experts outside the government were more explicit.
“If President Putin goes ahead with his apparent intention to annex Crimea, we’re going to have to sanction Russia, and they are going to have to retaliate, and it’s really going to screw up the P5-plus-one negotiations with Iran,” said Gary Samore, a former senior aide on nonproliferation on the National Security Council in President Obama’s first term. He is now executive director for research at Harvard’s Belfer Center for Science and International Affairs, as well as the president of United Against Nuclear Iran, a group that advocates strong sanctions against Iran until the nuclear dispute is resolved.
“The problem will be that Iran will feel much less pressured to make any concessions if they think the P5-plus-one are squabbling,” Mr. Samore said. “The Iranians will be watching and waiting; they are not inclined to make any concessions anyway, but they are going to be less inclined until there is a resolution” of the situation in Ukraine.
There had been no expectation a deal would be reached quickly even before the Ukraine crisis. A temporary nuclear agreement, known as the joint action plan, which was reached on Nov. 24 in Geneva and took effect on Jan. 20, limited Iran’s nuclear activities in exchange for some temporary sanctions relief from the West.
The temporary accord, which lasts six months and is renewable, was designed to give negotiators more latitude to reach a permanent agreement. It expires in July but is renewable.
But negotiators always hope to make headway on smaller points so that they can begin to attack the bigger points of difference, and it appears that the potential spillover from Ukraine tensions could make it difficult to make progress even on more minor issues, Western officials said. At the last meeting, they agreed on a framework for the talks and a schedule.
Foreign Minister Mohammad Javad Zarif of Iran, who leads the country’s negotiations with the P5-plus-one group, appeared to lower expectations for progress. Speaking in Tehran last weekend, Mr. Zarif said diplomats “don’t expect to reach a deal in this round of talks.”
He said that they would discuss both Iran’s planned heavy water reactor at Arak, which the West fears could eventually be used to reprocess plutonium into possible weapons fuel, and Iran’s uranium enrichment program.
The two sides are far apart, with Iran adamant about retaining its right to enrich uranium for peaceful purposes and the West adamant that it wants measures to prevent Iran from ever turning the country’s supply of low-enriched uranium into higher-enriched bomb-grade fuel.
Although Iran denies having any intention of making a nuclear weapon, evidence that it appeared to have begun developing long-range missiles capable of carrying a nuclear warhead and that it tried to hide some of its uranium enrichment facilities has made the West as well as Israel and Iran’s Sunni Arab neighbors suspicious.
As part of the temporary agreement reached in November, Iran agreed to reduce its stock of uranium enriched to close to 20 percent in return for moderate sanctions relief, including access to $4.2 billion in Iranian cash frozen in foreign banks.
The International Atomic Energy Agency, the United Nations monitor of the Nuclear Nonproliferation Treaty, verified in early March that Iran was complying with the temporary agreement.
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