Instead, Mr. Obama suggested that negotiators seek a solution that would seem "more acceptable" to Iran's political constituencies, while preserving leverage to force the government to abide by the deal. Rather than the timing and structure of sanctions relief, he said his priority was creating a system for reimposing the punitive measures if Iran is caught cheating.
"How sanctions are lessened, how we snap back sanctions if there's a violation, there are a lot of different mechanisms and ways to do that," Mr. Obama said at a White House news conference alongside the Italian prime minister, Matteo Renzi. The negotiators, Mr. Obama said, need to "find formulas that get to our main concerns while allowing the other side to make a presentation to their body politic that is more acceptable."
"Our main concern here is making sure that if Iran doesn't abide by its agreement, that we don't have to jump through a whole bunch of hoops in order to reinstate sanctions," Mr. Obama continued. "That's our main concern."
With Secretary of State John Kerry seated in front of him in the East Room, the president said: "And it will require some creative negotiations by John Kerry and others. And I'm confident we will be successful."
The dispute over sanctions has proved to be one of the biggest flash points as each side characterizes a framework agreement that has yet to be committed to writing. American officials long anticipated that Iran would portray the agreement in more favorable terms to its domestic audience, but the insistence on immediate sanctions relief underscored the challenges in translating the current understanding into a final accord by a June 30 deadline.
Mr. Obama's domestic critics have cited that uncertainty as evidence that he and his counterparts from Britain, France, Germany, Russia and China have not struck a good enough bargain. If sanctions are lifted at the start, they argue, Iran will not have an incentive to genuinely cut back its nuclear program.
Mohammed Javad Zarif, Iran's foreign minister, said Friday that the United States had diverged from the framework agreement reached on April 2 by publishing what the Americans called a fact sheet about its basic provisions. Contrary to the American assertion, Mr. Zarif said, there would be no phased removal of sanctions to ensure Iranian compliance.
Continue reading the main story Continue reading the main story "The United States for their own domestic reasons — and that's their right and prerogative — produced a fact sheet, which was not exactly what we adopted," Mr. Zarif told Euronews, a France-based broadcaster.
In his first extensive interview with a Western news organization since the agreement was reached, Mr. Zarif also raised the prospect of unlimited enrichment of Iranian atomic fuel if the talks did not achieve a final agreement by June 30 with all sanctions dropped.
While Iranian officials have always asserted that their nuclear program is peaceful — and Mr. Zarif did so again in the Euronews interview — he chose blunt language to describe what would happen if negotiations failed to produce a final agreement.
"We can have the path of confrontation, or we can have the path of cooperation," he said, speaking in English. "We cannot have a little bit of each. If we take the path of confrontation, the United States and the United Nations will continue with their sanctions, and Iran will continue with its enrichment program. Without any limitations."
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As for Mr. Obama, his aides said he was not trying to signal a change in policy with his comments at the news conference.
"He was emphasizing snapback" sanctions that could be reapplied quickly "and the fact that this will be a subject of intense negotiation," said a senior administration official, who insisted on anonymity to parse the president's words. "But we've always made clear the principle that sanctions relief will have to be phased and in response to Iranian actions, and that continues to be the case."
Negotiators will meet in Vienna next week to resume talks aimed at forging a final deal. Besides the sanctions issue, other areas of dispute include how much leeway international inspectors will have to visit suspected nuclear sites, including those on military bases, and how forthcoming Iran will have to be about any past work to design nuclear weapons.
Even as he has focused on concluding a deal with Iran, Mr. Obama has been maneuvering for room at home, where Republicans and many Democrats have been skeptical of his agreement. He said Friday that he would sign bipartisan legislation that would temporarily suspend his power to waive sanctions imposed by Congress while lawmakers review and possibly vote on any agreement.
Although he had vowed to veto an earlier version, he said the current draft was "a reasonable compromise" because it would not interfere with the negotiations. But he made clear that he remained bothered by what he initially saw as an intrusion into the president's authority to conduct foreign policy.
"I still have some concerns about the suggestion that that tradition was in some ways changing," he said. But the revised bill made clear that it was focused on congressionally imposed sanctions. "And that I think at least allows me to interpret the legislation in such a way that it is not sending a signal to future presidents that each and every time they're negotiating a political agreement, that they have to get a congressional authorization."
He also refrained from criticizing Russia for deciding to resume sales of S-300 antiaircraft batteries to Iran, which it had suspended for years. Such batteries worry military planners who say they could make it much more difficult for the United States or Israel to bomb Iran's nuclear facilities if the agreement breaks down.
Mr. Obama said he was "frankly surprised" that Russia had held back selling the weapons this long, but added that the decision buttressed his argument in favor of a deal because it showed that international solidarity could crumble.
"If it is perceived that we walked away from a fair deal that gives us assurances Iran doesn't get a nuclear weapon, then those international sanctions will fray," he said. "And it won't just be Russia or China. It will be some of our close allies."