Iran’s chief nuclear negotiator signaled progress at talks with six world powers Thursday on a deal to cap some of his country’s atomic programs in exchange for limited relief from sanctions stifling Iran’s economy, saying the six had accepted Tehran’s proposals on how to proceed.

U.S. officials said Secretary of State John Kerry will fly to Geneva today to participate in the negotiations — a last-minute decision that suggests a deal could be imminent.

A senior State Department official traveling with Kerry in Jordan said the secretary would come to Geneva “to help narrow differences in negotiations.” The official spoke on condition of anonymity because he was not authorized to release information about the Geneva visit.

Even if an agreement is reached, it would only be the start of a long process to reduce Iran’s potential nuclear threat, with no guarantee of ultimate success.

Still, a limited accord would mark a breakthrough after nearly a decade of mostly inconclusive talks focused on limiting, if not eliminating, Iranian atomic programs that could be turned from producing energy into making weapons.

Tehran’s chief nuclear negotiator, Abbas Araghchi, told Iranian state TV that the six — the United States, Russia, China, Britain, France and Germany — “clearly said that they accept the proposed framework by Iran.” He later told CNN that he thinks negotiators at the table are now “ready to start drafting” an accord that outlines specific steps to be taken.

Though Araghchi described the negotiations as “very difficult,” he told Iranian state TV that he expected agreement on details by today, the last scheduled round of the current talks.

The upbeat comments suggested that negotiators in Geneva were moving from broad discussions over a nuclear deal to details meant to limit Tehran’s ability to make atomic weapons. In return, Iran would start getting relief from sanctions that have hit its economy hard.

U.S. officials said Kerry will travel to the Geneva talks after a brief stop in Israel, where he will hold a third meeting with Israeli Prime Minister Benjamin Netanyahu, who has spoken out against any limited deal that would allow the Iranians sanctions relief.

In Geneva, Kerry is expected to meet with the European Union’s top diplomat, Catherine Ashton, and Iranian Foreign Minister Mohammad Javad Zarif, the officials said. They spoke on condition of anonymity because they were not authorized to comment on the schedule.

The talks are primarily focused on the size and output of Iran’s enrichment program, which can create both reactor fuel and weapons-grade material suitable for a nuclear bomb. Iran insists it is pursuing only nuclear energy, medical treatments and research, but the United States and its allies fear that Iran could turn this material into the fissile core of nuclear warheads.

President Barack Obama, in an interview with NBC on Thursday, said the negotiations are less about easing sanctions than about how Iran begins to assure the world that it is not developing nuclear weapons.

“Our job is to put in place mechanisms where we can verify what they’re doing and not doing when it comes to their nuclear program,” Obama said.

Warily watching from the sidelines, Israel warned against a partial agreement that foresees lifting sanctions now instead of waiting for a rigorous final accord that eliminates any possibility of Iran making nuclear weapons.