Iran needs stronger guarantees from the United States to revive a landmark agreement limiting its nuclear program, Foreign Minister Hossein Amirabdollahian said on Wednesday.

"Iran is carefully reviewing the EU-drafted text ... We need stronger guarantees from the other party to have a sustainable deal," he said during a trip to Russia.

The initial accord was struck in 2015 between Iran and six world powers — Germany, China, France, Britain, the US and Russia. Under that deal, Tehran agreed to curb its nuclear program in return for sanctions relief. But the pact fell apart after former US President Donald Trump withdrew unilaterally in 2018.

The EU, which is seeking to salvage the agreement, put forward what it called a final text in early August following months of indirect talks between Tehran and Washington in Vienna. Since then, both Iran and the US have responded with a series of proposed changes.

Amirabdollahian said Tehran was reviewing Washington's response. He did not elaborate on what he meant by "stronger guarantees," but during the lengthy negotiations with Washington, Tehran demanded US assurances that no future American president would abandon the deal as Trump did.

White House national security spokesman John Kirby said they were waiting for an official response from Iran, and that the US had not seen Amirabdollahian's remarks.

"So I don't know what guarantees he's talking about," Kirby told reporters. "While we are ... cautiously optimistic, we are also pragmatic and clear-eyed and we realize that there's still gaps."

EU foreign policy chief hopeful on deal in 'days'

Despite the latest diplomatic wrangling, the EU's foreign policy chief said he had recieved "reasonable" responses to the EU proposed text from Iran and the US.

"I am hoping that in the coming days we are not going to lose this momentum and we can close the deal," Josep Borrell said after an informal meeting of EU foreign ministers in Prague.

"It's clear that there is a common ground, that we have an agreement that takes into account, I think, everyone's concerns," he said.

The EU's draft agreement would see limits imposed on Iran's nuclear activities and pave the way for the US to lift sanctions and allow Iranian energy exports back onto world markets.

Biden, Lapid discuss Iran nuclear deal

US President Joe Biden spoke with Israeli Prime Minister Yair Lapid about the deal on Wednesday, a White House official said.

Lapid had previously stressed that he is not fundamentally opposed to an agreement with Iran.

However, he believes the current version of the deal is "bad."

Israel is calling for an agreement that provides for stricter monitoring of Iran's nuclear program and a restriction of its missile program. This is because Israel sees itself existentially threatened by Iran.

In its own readout of the leaders' call, Lapid's office said they "spoke at length about the negotiations on a nuclear agreement, and their shared commitment to stopping Iran's progress towards a nuclear weapon."

lo/nm (Reuters, AFP, dpa)