GENEVA: Iran and six major powers appear close to a deal on Iran’s nuclear program, with US Secretary of State John Kerry set to join the talks Friday, a late-breaking surprise here. It could signal the beginning of the end of the decade-old crisis sparked by fears Iran is trying to develop nuclear weapons.

US officials refused to comment after a day of talks during which Iran met bilaterally with Britain, France and Germany, who represent the European Union. Then they met with China, Russia and the United States. A Western official said there was a “different feel” to the talks than in previous negotiations. “People were running up and down corridors, making phone calls,” as the seven nations worked on a joint statement that would mark a first step towards resolving the crisis.

Iranian Deputy Foreign Minister Abbas Araghchi, who leads the Iranian delegation with Iranian Foreign Minister Javad Zarif, confidently said he expected an agreement “today, tomorrow or in the next meeting.” The two sides “exchanged our views on the three categories that we are negotiating – a common objective, a first step and a final step” in giving guarantees that Iran will not seek the bomb. The first step would be “a set of concrete measures that could be done by both sides,” he told reporters. He said the two sides were talking about concrete measures and not just about how to negotiate, as has been the case for most agreements in the past.

Neither Araghchi or Western officials would provide details, but it is believed a first step would involve Iran suspending the enrichment of uranium to a medium level that is close to weapon-grade. Iran might also reduce its low-level enrichment, which makes what can be fuel for civilian power reactors but when refined further for atom bombs. A senior US official said here earlier in the week that the US goal was to strike a deal that kept Iran from expanding its nuclear work, and that this should be through concrete, verifiable measures. Once the Iranian nuclear program is reined in, there would be time for talks on a final settlement.

Iran wants significant sanctions relief in return for a first step, but the United States has made clear that lifting the punitive measures that limit Iranian oil sales and block Iran from international banking (making it very difficult for them to trade), will be done gradually and not all at once. A senior Iranian official seemed to signal Iran’s acceptance of this when he told Breaking Defense that there would be sanctions relief in the first step and the final step.

Iran wants to have its right to enrich uranium acknowledged. This will almost certainly be dealt with in the final step, although it is not yet clear how.

There are still gaps between Iran and the United States, and a deal is not 100 percent certain. But Kerry’s coming to the talk — confirmed by the State Department shortly after midnight here — signals just how close the two sides have gotten, after a decade of no progress. All seems to have changed since the August election of new Iranian President Hassan Rouhani. Rouhani pledged to defuse the nuclear crisis and get sanctions lifted which are destroying the Iranian economy.

A Western official said Kerry is “very good at narrowing gaps,” an important reason why he was joining the talks at this stage. Kerry had met for a half-hour chat with Iranian Foreign Minister Zarif in New York in September in what was then the highest-level contact between the United States and Iran since the Islamic revolution in 1979. This was followed by a direct phone call between Rouhani and American President Barack Obama. The nuclear talks then continued at a senior foreign ministry level, with it being clear that Kerry would join the talks once a settlement loomed.

Now Iran and the United States, as well as the other negotiating nations  — Britain, China, France, Germany and Russia — are “very close” to striking a deal, the Western official said. The official said the Iranians wanted at this point to move quickly because they “need relief from sanctions and there’s only one way to get relief,” which is a deal.

A sign of just how close they are were the sharp reactions Thursday from Israeli Prime Minister Benjamin Netanyahu and hardliners in the U.S. Congress. Netanyahu, who wants Iran to cease all enrichment activities and not just some, called the possible deal a “historic” mistake. Tim Johnson, chairman of the Senate Banking Committee, said he would move ahead and present a severe new sanctions bill.

Officials from both the United States and Iran have warned that increased sanctions at this point could scuttle the talks.