High-ranking diplomats from China, Germany, France, Russia and the UK made progress in talks with Iran on Saturday in Vienna that focused on bringing Washington and Tehran back into compliance with their landmark 2015 deal.

Russia's top representative at the talks, Mikhail Ulyanov, said on Twitter that members of the Joint Comprehensive Plan of Action (JCPOA), the agreement that saw international economic sanctions on Iran lifted in exchange for Tehran not advancing its nuclear weapons program, "noted today the indisputable progress made at the Vienna talks on restoration of the nuclear deal."

A diplomatic source for the trio of European nations at the talks, the UK, Germany and France, said the discussions took place amid a "serious and focused atmosphere despite outside turbulence."

"We have yet to come to an understanding on the most critical points," a European source said. "Success is by no means guaranteed, but not impossible."

Negotiators have been meeting in Austria for nearly one month in an attempt to bring the United States and Iran back to compliance with the terms of the agreement.

Outside issues

The US did not have a representative at the meeting because the country pulled out of the deal in 2018 under then-President Donald Trump. Current President Joe Biden wants to rejoin the deal, however, and a US delegation in Vienna took part in indirect talks with Iran.

US National Security Adviser Jake Sullivan said Friday that the Vienna talks were in "an unclear place," implying it was uncertain they would ultimately lead to an agreement.

Biden has called on Tehran to roll back its nuclear program before the US ends its sanctions on the country. But Iran has insisted sanctions must be lifted before it gives up the development of its nuclear capabilities.

Another issue surrounding the talks in Vienna stems from a recent attack on Iran's Natanz nuclear site. The attack, which caused an unknown amount of damage, caused Iran to retaliate by enriching small amounts of uranium even further. The uranium was enriched to 60% purity, its highest ever, far beyond the limit allowed under the deal.

Still work to do

After Saturday's meeting, the representatives were set to return to their respective capitals and reconvene next Friday, Iran's Foreign Ministry said in a statement.

"Considering the commission's previous decision regarding speeding up the talks process, this week's talks continued quickly in bilateral format and the sides tried to minimize disagreements regarding the texts," said the ministry.

A European diplomatic source told Reuters news agency that there was still considerable work to be done.

"We have much work, and little time left. Against that background, we would have hoped for more progress this week," said the source.

"We have yet to come to an understanding on the most critical points," Russia's Ulyanov told reporters after the third round of meetings. "We should not expect breakthroughs in the days to come.

"We need simply to continue diplomatic, day-to-day work, and we have all the reasons to expect that the outcome, [the] final outcome, will be successful and it will come quite soon, in a few weeks," he added.

kbd/sms (AP, AFP, dpa, Reuters)