Iran says substantial progress has been made in talks with world powers to revive a landmark nuclear deal, but critical issues remain unresolved.
Iran and the six powers have been holding talks in Vienna since April to work out steps that Tehran and Washington must take on sanctions and nuclear activities to return to full compliance with the 2015 nuclear agreement.
"Each round of talks in Vienna could have been the final round. We should not rush. We have made significant progress but key issues remain," Foreign Ministry spokesman Saeed Khatibzadeh told a televised weekly news conference in Tehran on May 31.
"There has been no stalemate on the Vienna talks," he added.
Speaking to state television from the Austrian capital, Iran's top nuclear negotiator, Abbas Araqchi, said the negotiations were "very complex" and that the sides "have now reached the main issues of dispute."
Under the accord, known as the Joint Comprehensive Plan of Action, Iran pledged to curb its nuclear activities in exchange for an easing of international sanctions.
The deal was put on hold three years ago after then-U.S. President Donald Trump pulled Washington out of the pact and reimposed crippling sanctions on Iran's economy.
In response, Tehran has steadily overstepped the agreement's limits on its nuclear program designed to make it harder to develop an atomic bomb -- an ambition Tehran denies.
President Joe Biden, who was inaugurated in January, has said the United States will return to the pact if Tehran first resumes compliance with its strict limits on uranium enrichment, a process that could allow Iran to build nuclear weapons.
"All sanctions should be lifted and then it should be verified by Iran...then we will reverse our nuclear steps," Khatibzadeh said.
An unnamed diplomat, briefed by Western officials involved in the talks, said that "an agreement that would clarify the obligations of Tehran and Washington to move forward" will be announced in Vienna this week.