Iran and the U.S. are close to a deal that will revive the 2015 nuclear accord, a top European Union official said after the latest talks in Vienna, in the clearest sign yet of major progress toward ending a confrontation that’s convulsed the Persian Gulf.

The possibility of a breakthrough is being closely watched by oil traders and Gulf states trying to determine how quickly Iran might be able to resume major crude exports and do business with the world.

“We have made substantial progress over the last 10 days but there are still things to be worked on and we will reconvene next week,” said Enrique Mora, the EU official in charge of coordinating diplomacy in the Austrian capital. “The spirit of compromise is high,” he said. “I am quite sure there will be a final agreement, not far from here.”

Iran has been under punishing sanctions since former U.S. President Donald Trump abandoned the landmark accord in 2018. Diplomats from China, Europe, Russia and the U.S. were in Vienna this week for a fourth round of talks that are intended to lift those sanctions in return for Iran reversing its moves to ramp up the country’s enrichment activity.

Iran’s top negotiator was also upbeat.

“We’ve reached a framework on an agreement,” said Abbas Araghchi, deputy foreign minister, adding that there were still some differences on key issues and teams would return to their capitals for consultations. Still, “we’re hopeful that next week, when talks start again, the delegations will have made their own decisions to reach an agreement,” he said.

The nuclear dispute between Washington and Tehran has roiled the wider Middle East, fueling conflicts where Iran and American allies are on opposing sides, and precipitating attacks on shipping in key waterways.

Mora said that Iran and the International Atomic Energy Agency are likely to extend an interim agreement allowing nuclear inspections that was due to expire this weekend. The Spanish diplomat said his Iranian counterparts appeared “fully committed” to reaching a compromise and were “putting on the table what they need to reach an agreement.”

Iran’s President Hassan Rouhani -- who championed the original agreement and is several months away from leaving office -- is under pressure from a hardline parliament that’s hostile to the nuclear deal. Conservative lawmakers are demanding Iran continue expanding its nuclear work while the U.S. is out of the accord.

Mora said he expects all parties to return to the original 2015 agreement before Iran’s presidential elections on June 18.