GENEVA — With only a month to go before a deadline for finalizing a nuclear accord with Iran, Secretary of State John F. Kerry began a major push Saturday to conclude the agreement.
Kerry and Mohammad Javad Zarif, the Iranian foreign minister, met Saturday at a hotel here for talks. It was the first high-level negotiating round since the two sides settled on the outline of an agreement on April 2 in Lausanne, Switzerland.
It was unclear how much progress Kerry and Zarif made before the Iranian delegation began leaving. Lower-level officials are expected to meet again in Vienna next week.
With important issues unresolved, analysts have begun to question the wisdom of negotiating against a deadline, saying it may work to Iran’s advantage by building pressure on the United States and its negotiating partners to make concessions.
“It is a tall order for them to finish by the end of June, especially to get the technical annexes done in sufficient detail to avoid implementation problems,” said Robert J. Einhorn, who served on the US delegation to the Iran talks until 2013. “The negotiators should take whatever time they need, even if it means working past June 30.”
Gary Samore, who was the senior National Security Council official on weapons of mass destruction during President Obama’s first term, said US officials should be prepared to negotiate through the summer.
“Tactically, it is better to extend the talks to demonstrate that we aren’t desperate for a deal at any cost,” said Samore, who is a member of the group United Against Nuclear Iran.
Kerry, however, has long spoken of the importance of deadlines, arguing that they are the only way to get officials on both sides to make the tough decisions that are needed to seal an accord.
“We’ve often seen during these talks that deadlines are action-forcing mechanisms,” said a State Department official who declined to be identified under the agency’s procedures for briefing reporters. “We do believe we can get it done by the 30th.”
The official said Kerry had cleared his schedule for most of June for the talks.
To accelerate the talks, the US energy secretary, Ernest J. Moniz, who played an instrumental role in the earlier negotiations in Lausanne, flew here at Kerry’s request.
The remaining obstacles include the need to agree on effective verification measures, on a schedule for lifting economic sanctions on Iran, and on what research and development Iran would be allowed to conduct on advanced centrifuges, which are used to enrich uranium.
The resolution of such questions will help determine how advanced Iran’s nuclear program might be when an accord expires.
The Obama administration has argued that the deal under negotiation would extend to a year, from the current two or three months, the amount of time that it would take Iran to produce enough nuclear material for a bomb. But the provisions to achieve that yearlong “breakout time” would be eased after the first decade of an agreement, though the implications of that remain unclear.
In an April interview with NPR, Obama said that breakout time might shrink “almost down to zero” in the final few years of a 15-year agreement.
He then argued that the agreement would still be worth it, and other officials say that the final breakout time might not be so short, depending on the terms of an agreement. What latitude Iran will have to develop and install new enrichment technology in the last years of an accord will depend on arrangements that have yet to be enumerated.
Other key questions relate to how to verify that Iran is following the agreement and address suspicions that it has already conducted secret nuclear weapons research. After the Lausanne talks, Iran’s supreme leader, Ayatollah Ali Khamenei, declared that neither inspections of Iranian military sites nor interviews with Iran’s nuclear scientists would be allowed.
That prompted concerns that Iran might be backtracking from understandings sketched out in the earlier talks. Those worries were only partly eased when Abbas Araqchi, Iran’s deputy foreign minister, said his country had agreed to “managed access” in which inspectors could take samples “from the vicinity of military sites.” And on Saturday, he said that allowing Iran’s scientists to be interviewed was “generally off the table.”
Experts say that wide-ranging inspections are needed to guard against cheating. They also say that the International Atomic Energy Agency needs to interview Iranian scientists to resolve questions about Iran’s suspected work on nuclear weapons designs and tests of weapons components — what the agency calls the “possible military dimensions” of the Iranian program.
The State Department official said that the two sides had made some headway in Lausanne on this issue by agreeing to develop a “list of people and places for access” but acknowledged that key details had yet to be settled.
“We didn’t agree on the list, but we agreed to undertake a process to develop that list,” the official said.