European Union foreign policy chief Josep Borrell.© Stephanie Lecocq/AP European Union foreign policy chief Josep Borrell.The European Union’s foreign affairs chief Josep Borrell announced the decision to “pause” the talks in a tweet, citing “external factors” for the decision to break off the talks. Negotiators for the seven countries involved have spent most of the past year huddled in Vienna 2015 trying to find ways to revive the 2015 nuclear deal following President Donald Trump’s decision to withdraw the United States from the agreement.

Diplomats said Borrell was referring to Russia’s eleventh-hour demand first raised last Saturday for U.S. sanctions relief to be applied to its future dealings with Iran as a condition for participating in a revived deal.

But the open-ended pause could also potentially signal a break from which there is no return, putting to rest any hope that restoring the deal will be possible.A final text for a new agreement is “essentially ready and on the table,” Borrell said, adding that he and his team would remain in contact with all the participants to overcome the remaining obstacles and finalize an agreement.

“It’s certainly serious. If you lose momentum at this late stage the dynamics shift in ways that it could become impossible to resume the talks,” said Esfandyar Batmanghelidj of the European Council on Foreign Relations.

The talks in Vienna had been focused on laying out a timetable to bring the United States and Iran back into compliance with the 2015 Joint Coordinated Plan of Action, as the nuclear deal is known. Under the new agreement, the United States would be expected to lift the harsh new sanctions imposed after Trump withdrew, and Iran would be required to dial back advances made in the meantime to its nuclear program.

A deal was so close that a podium for the final ceremonies had been erected in the Palais Coburg hotel where the talks were held. In recent weeks Iran had increasingly signaled its willingness to finalize the arrangement, diplomats say.

But the outbreak of the Ukraine war has shifted the geopolitical backdrop to the negotiations, and it is now possible that the fate of the Iran talks will effectively become hostage to the course of the war, diplomats say.

Informal consultations are expected to continue, negotiators say, to include exploring ways to finalize the deal without Russia — something that would be complicated but not impossible. Russia plays a key role in the deal’s implementation as the country responsible for shipping out and storing Iran’s excess stocks of enriched uranium, for which another destination would have to be found.

Iran is also expected to try to exert quiet pressure on Moscow to relax its demands. But Tehran has also made it clear that Iran feels it can’t risk a public rift with Russia by turning its back on Russian concerns, a senior Western diplomat said.

The talks have involved diplomats from Britain, France, Germany and China as well as Iran, the United States and Russia, with the Iranian and U.S. delegations meeting their counterparts in separate hotels because Iran has refused to engage in direct talks with the Americans.

Iran nuclear talks are suspended amid new Russian demands (msn.com)