The United States and European Union both said Tuesday that more work was needed to revive the 2015 deal on Iran's nuclear program, although Tehran reported progress after the latest diplomacy, AFP reports.
The talks aimed at returning the United States to the 2015 deal took their second break, with US envoy Rob Malley set to return to Washington for the rest of the week, according to the news agency.
EU diplomat Enrique Mora hailed "progress made over the last two weeks" but said "ongoing challenges" remained to put the accord back on track.
Iranian President Hassan Rouhani, however, said the "negotiations have achieved 60-70 percent progress."
"If the Americans act honestly, we will reach a conclusion in little time," Rouhani said, as quoted by state news agency IRNA.
State Department spokesman Ned Price, asked about Rouhani's optimism, was more cautious.
"Yes, there has been some progress but there remains a long road ahead," Price told reporters in Washington, according to AFP.
"I think it's fair to say that we have more road ahead of us than we do in the rearview mirror," he added.
It has continued to do so even as current US President Joe Biden has indicated a desire to return to the deal.
Iranian negotiator Abbas Araghchi announced a week ago that Iran would begin enriching uranium to 60% purity, its highest level to date in response to the blackout and explosion which occurred at the Natanz nuclear facility over the weekend.
The move would shorten Iran's breakout time to being able to construct a nuclear weapon.
Despite Iran’s announcement on the uranium enrichment, the White House later said it remains committed to nuclear negotiations with Iran.
Diplomats from Britain, China, France, Germany, Iran and Russia have been meeting since early this month in a luxury Vienna hotel, while US diplomats are participating indirectly in the talks from a nearby hotel.
Talks are set to resume next week, according to an EU statement.