The United States and Iran reported progress in their latest round of nuclear talks yesterday and agreed to meet again next week as they pursue a deal that could help ease soaring Middle East tensions.

A US official called the talks "positive and productive", and Iran's top diplomat said the two sides will study how to narrow their differences on a range of subjects before next week's fourth round.

The highest-level contact in years between the long-time foes is targeting a new deal that would stop Iran from developing nuclear weapons -- an objective Tehran denies pursuing -- in return for relief from sanctions.

"There is still much to do, but further progress was made on getting to a deal," the senior US official said on condition of anonymity, adding that the next talks would be in Europe.

Iranian Foreign Minister Abbas Araghchi called yesterday's talks, which included technical-level teams for the first time, "serious and businesslike".

"There are differences both in the major issues and in the details," he told Iranian state TV.

"Until the next meeting, further studies are to be conducted in the capitals on how to reduce the differences."

Araghchi added: "I think our progress has been good so far. I am satisfied with the process of the negotiation and its speed. I think it is proceeding well and satisfactorily."

US special envoy Steve Witkoff again led the American delegation while Michael Anton, the State Department's head of policy planning, headed the US expert-level negotiators.

Deputy foreign ministers Kazem Gharibabadi and Majid Takht-Ravanchi led Tehran's technical team, according to Iran's Tasnim news agency.

The delegations were in separate rooms and communicated in writing via the hosts, Iranian foreign ministry spokesperson Esmaeil Baqaei and Araghchi said.

Iran's defence and missile capabilities were not discussed, Baqaei told state TV, while an Iranian negotiator said the talks were "uniquely about sanctions and nuclear questions", according to Tasnim.

Araghchi had earlier expressed "cautious optimism", saying this week: "If the sole demand by the US is for Iran to not possess nuclear weapons, this demand is achievable".