Enrique Mora, deputy secretary-general of the European External Action Service, speaks to reporters after a meeting of the Joint Comprehensive Plan of Action (JCPOA) Joint Commission in Vienna, Austria, on Dec 3, 2021. (GUO CHEN / XINHUA)

BRUSSELS/WASHINGTON - The European Union is assessing Iran's response to what the bloc has called its "final" proposal to save a 2015 nuclear deal, and consulting with the United States, an EU spokesperson said on Tuesday.

"For the moment, we are studying it and we are consulting with the other JCPOA participants and the US on the way forward," the spokesperson told reporters in Brussels, referring to the nuclear deal by the official abbreviation JCPOA.

She declined to give a time frame for any reaction by the EU who is coordinating the negotiations in Vienna.

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The US State Department said on Monday that the only way to revive the 2015 Iran nuclear deal is for Tehran to abandon its extraneous demands, saying Washington believes everything that can be negotiated already has been

After 16 months of fitful, indirect US-Iranian talks, with the EU shuttling between the parties, a senior EU official said on Aug 8 the bloc had laid down a "final" offer and expected a response within a "very, very few weeks."

The US State Department said on Monday that the only way to revive the 2015 Iran nuclear deal is for Tehran to abandon its extraneous demands, saying Washington believes everything that can be negotiated already has been.

Iran responded to the proposal late on Monday but neither Tehran nor the EU provided any details on the content of the reply. 

Iran's foreign minister had called on the US to show flexibility to resolve three remaining issues, suggesting Tehran's response would not be a final acceptance or rejection.

Washington has said it is ready to quickly seal a deal to restore the 2015 accord on the basis of the EU proposals.

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Diplomats and officials have told Reuters that whether or not Tehran and Washington accept the EU's "final" offer, neither is likely to declare the pact dead because keeping it alive serves both sides' interests.

The stakes are high, since failure in the nuclear negotiations would carry the risk of a fresh regional war with Israel threatening military action against Iran if diplomacy fails to prevent Tehran from developing a nuclear weapons capability.

Iran, which has long denied having such ambition, has warned of a "crushing" response to any Israeli attack.

In 2018, then-president Donald Trump reneged on the nuclear deal reached before he took office, calling it too soft on Iran, and reimposed harsh US sanctions, spurring the Islamic Republic to begin breaching its limits on uranium enrichment.