Russia’s announcement, which could torpedo months of intensive indirect talks between Tehran and Washington in Vienna, came shortly after Tehran said it had agreed a roadmap with the nuclear watchdog UN to resolve outstanding issues that could help secure the nuclear pact.

“The Russians had put this request on the table (at the talks in Vienna) two days ago. It is understood that by changing its position in the talks in Vienna, Russia wants to protect its interests in other places. This decision is not constructive for the Vienna nuclear talks,” the Iranian official said in Tehran.

Demanding written guarantees from the United States that Western sanctions imposed on Russia over the conflict in Ukraine would not harm its cooperation with Iran, Russian Foreign Minister Sergei Lavrov said the limitations had become a cornerstone. stumbling block over Iran nuclear deal, warning the West that Russian national interests must be taken into account.

Lavrov said sanctions against Russia over the conflict in Ukraine had created a “problem” from Moscow’s perspective.

When asked if Russia’s request would harm 11 months of talks between Tehran and world powers, including Russia, Iran Project Director at the International Crisis Group, Ali Vaez, replied: “Not yet. But it is impossible to separate the two crises any longer.”

“The United States can issue waivers for work related to the transfer of excess fissile material to Russia. But this is a sign that the mixing of the two issues has begun,” Vaez said.

Two diplomats, one of whom is not directly involved in the talks, said China had also demanded written guarantees that its companies doing business in Iran would not be affected by US sanctions.

Such demands can complicate efforts to seal a nuclear deal at a time when a deal seemed likely.

All parties involved in the Vienna talks said on Friday they were close to reaching an agreement.

“We have agreed to provide the IAEA by (the Iranian month of) Khordad (May 21) with documents related to outstanding issues between Tehran and the agency,” Iran’s nuclear chief Mohammad Eslami said during the meeting. a joint press conference with the International Atomic Energy Agency (IAEA). ) chef Rafael Grossi.

Grossi arrived in Tehran on Friday evening to discuss one of the last thorny issues blocking the revival of the pact, which in exchange for lifting economic sanctions limited Iran’s uranium enrichment, making it more difficult for Tehran the development of materials for nuclear weapons.

“It’s important to have this understanding…to work together, to work very intensively,” Grossi said at the televised press conference.

“Without resolving these (outstanding) issues, efforts to revive the JCPOA may not be possible.”

A major sticking point in the talks, Tehran wants the issue of traces of uranium discovered at several ancient but undeclared sites in Iran to be closed. Western powers say it is a separate issue from the deal, to which the IAEA is not a party, several officials told Reuters.

Grossi, who also spoke with Iran’s foreign minister before returning to Vienna on Saturday, said “there are still issues that need to be addressed by Iran.”

The IAEA has demanded answers from Iran on how the traces of uranium got there – a topic often referred to as “outstanding safeguards issues”.

Grossi’s trip has raised hopes that a deal with the IAEA will potentially pave the way for reviving the nuclear pact scrapped in 2018 by former US President Donald Trump, who also reimposed heavy sanctions on the Iran.

Since 2019, Tehran has exceeded the agreement’s nuclear limits and gone far beyond them, replenishing stockpiles of enriched uranium, refining it to higher fissile purity and installing advanced centrifuges to speed up production. Iran denies ever having sought to acquire nuclear weapons.

(Additional reporting by Guy Faulconbridge in London: Writing by Parisa Hafezi; Editing by Michael Georgy, William Mallard, Catherine Evans, William Maclean and Louise Heavens)

By Parisa Hafezi and Francois Murphy