“The technical group will be back, I believe, on the 29th or the 30th… I believe they’re going back to Switzerland, if I’m not mistaken,” Rubio said.

Speaking during a tour of Gulf countries, Rubio stressed that Washington would coordinate closely with its regional partners as negotiations with Tehran move forward.

“We’re going to be completely aligned with our partners in the Gulf. That’s why we’re meeting with all of them tomorrow,” he said, adding the US would “engage them on conversations about every decision that’s made with regards to this negotiation”.

Rubio also said there was broad international opposition to any attempt by Iran to impose transit fees on vessels using the strategically important Strait of Hormuz, a key global energy shipping route.

“I know of no country on the planet that supports tolling or fees for the use of the strait,” Rubio said.

The remarks came as the United States seeks to reassure Gulf allies affected by the recent regional conflict while advancing diplomatic efforts aimed at establishing a permanent framework for stability between Washington and Tehran.