International and Iranian diplomats will meet this Saturday in Istanbul for negotiations on Iran’s nuclear program, for the first time in 15 months. Though the talks nearly fell through because of last-minute Iranian objections over the venue, the United States, United Kingdom, France, Germany, Russia, and China will come together with Iranian nuclear negotiators to see if Tehran is prepared to seriously consider curbing its most sensitive nuclear activities. The meeting is a key test of what President Obama has admitted is a “closing” window of time to determine if concerns about Iran’s nuclear bid can be resolved diplomatically—or not.Over the past week, there were clear signs that a kind of pre-negotiation had already begun. Statements by U.S. officials have focused largely on whether Iran can be persuaded to stop enriching its uranium to 20 percent purity—which, if Iran decided to, could be further enriched to 90 percent purity, or “weapons grade,” within several months—and remove the 20 percent enriched uranium stockpile already in its possession. Secretary of State Hillary Clinton said in Istanbul on April 1 that Iran can prove that it does not intend to make nuclear weapons “by ending … the enrichment of … uranium to 20 percent; by shipping out such highly enriched uranium out of the country, and by opening up to constant inspections.”Obama Administration officials also told the New York Times Saturday that the United States would ask Iran to stop operations at the underground Fordo enrichment plant—a highly fortified facility near Qom built deep into a mountain where Iran has launched both lower-level 3.5 percent and 20 percent enrichment activities earlier this year, according to a March report by the International Atomic Energy Agency. Israel is highly concerned that the facility is buried so deep that air strikes may not be capable of destroying it.Meantime, while the Iranians formally rejected any “preconditions” on this weekend’s talks, they’ve nevertheless signaled possible willingness to compromise on their higher-level enrichment activities. “Once the necessary fuel is obtained, we will scale back production [of 20 percent enrichment] and maybe even convert it to 3.5 percent,” Iran’s hardline nuclear chief Fereydoon Abbasi Davani told Iranian media Monday.The Iranians “are dangling” a possible compromise on 20 percent enrichment, Suzanne Maloney, a former State Department Iran expert now with the Brookings Institution, said Tuesday. While Maloney believes there’s a “fighting chance” to come to some sort of an interim compromise, she argued that there are many reasons to be pessimistic about the prospects for a broader diplomatic resolution with Iran. “There’s no evidence [the Iranian] Supreme Leader has come to the conclusion that the crisis needs to be resolved. He believes they can ride out the sanctions and is implacably opposed to a deal that would bring closer rapprochement with Washington,” she said.“No one should go into this weekend with the expectation that there will be a light-bulb moment for either side, or a clear glide path of sustained dialogue,” Maloney added. “That would be the best outcome.”Few analysts I spoke to expected the day-long Istanbul talks to be sufficient time to hammer out any sort of agreement. They suggested that Western negotiators may be looking to Istanbul as an opportunity to observe Iranian negotiators’ body language and see if there is receptivity for further meetings in the coming weeks.“I think there will be an effort to tell Iran, ‘OK, with Israel in the picture we have until June for a diplomatic roadmap to be agreed to in principle,’ ” Mark Hibbs, an expert at the Carnegie Endowment for International Peace’s Nuclear Policy Program, wrote in an email. Why the June time frame? Presumably because by that point, if Iran has not agreed to some measure that significantly eases Israeli concerns, it would be very hard for Washington to continue to advocate for negotiations.Afshon Ostovar, an Iran analyst with the Center for Naval Analysis, told me on Monday that the Obama Administration is trying to get sufficient concessions from Iran to ward off the prospect of an Israeli military strike this year. “Obama is trying to ensure that there is not an Israeli attack before [the U.S. presidential] election,” Ostovar said. “If they can get the Iranians to cooperate enough, then half the problem is solved. And [the administration] can push more forcefully in either direction”—sanctions relief, or more pressure on Iran with greater political flexibility—after November.Israeli officials, for their part, have expressed deep skepticism about Iranian intentions, even as they’ve laid out the conditions they would need Iran to agree to.“We told our American friends as well as the Europeans that we would have expected the threshold for successful negotiation to be clear,” Israeli Defense Minister Ehud Barak told CNN’s Fareed Zakaria Sunday. On Barak’s list: that Iran halt its 20 percent uranium enrichment activities, send out its stockpile of 20 percent enriched uranium to another country, send out most of its stockpile of 3.5 percent lower enriched uranium, and dismantle the Fordo enrichment facility.If such conditions are met, Barak said, “It would be a different regime.”Analysts said that observers shouldn’t take the telegraphed positions of any side as expected outcomes of the talks, but opening bids. “It’s not black or white, there are degrees of what do they get,” said Patrick Clawson, deputy director of research at the Washington Institute for Near East Policy, in an interview Monday. “This is how to go into negotiations, don’t tell what you are prepared to give.”***Like this article? Sign up for our Daily Digest to get Tablet Magazine’s new content in your inbox each morning.Laura Rozen reports on foreign policy from Washington, D.C. She is a former senior policy reporter for Politico and Foreign Policy. Follow her on Twitter @LRozen.