By John Irish and Francois Murphy

VIENNA: Iran will not back down on its red lines in nuclear talks with major powers, President Ebrahim Raisi said on Tuesday, as the United States and France warned there was little time left to revive their 2015 accord.

Eleven months of negotiations to restore the deal which lifted sanctions on Iran in return for curbs on its nuclear programme have reached their final stages. The European Union has said Washington and Tehran must now take the political decisions needed for agreement.

Iran has sought to remove all sanctions and it wants guarantees from the United States that it will not abandon the agreement once more, after then-U.S. President Donald Trump walked out of the deal in 2018 and reimposed sanctions.

Iran's top negotiator, Ali Bagheri Kani, unexpectedly returned to Tehran on Monday for consultations. A European and an Iranian official said he is expected, for now, to be back in Vienna on Wednesday.

"The government pursues nuclear negotiations in full accordance with the principles and framework set by the Supreme Leader," Raisi said, referring to Ayatollah Ali Khamenei, who has the final say in Tehran's decision.

"It has not and will not back down on any of these red lines," the semi-official Fars news agency quoted him as saying.

Talks coordinator Enrique Mora of the European Union said on Monday that the political decisions needed to conclude the negotiations successfully must be taken in the next few days.

The United States and France echoed that urgency.

"There is some but very little time remaining for steadfast diplomacy to put us on the collective path to a mutual return to full implementation" of the accord, a U.S. statement to the United Nations nuclear watchdog's Board of Governors said.

France, another of the parties to the Vienna talks, said further delays could jeopardise the chances of reaching agreement.

"We are very close to an agreement. It is essential we conclude while we still can," French Foreign Ministry spokeswoman Anne-Claire Legendre told reporters in a daily briefing. "We are concerned by the risks that further delays could weigh on the possibility of concluding."

'New era'

The United States said success would mark a "new era in our approach to Iran’s nuclear programme", although Central Intelligence Agency director William Burns cautioned that whether or not a deal is reached, challenges would persist.

Diplomats say several differences still need to be overcome in the talks, which were also hit by a last-minute demand from Russia for a guarantee from the United States that Russian trade, investment and military-technical cooperation with Iran would not be hindered by sanctions over its invasion of Ukraine.

U.S. Secretary of State Antony Blinken played down the issue during a visit to Estonia. "Russia continues to be engaged in those efforts and it has its own interest in ensuring that Iran is not able to acquire a nuclear weapon," Blinken said.

However, in an apparent reference to Moscow's demands, Legendre said France, Britain and Germany called on all parties to "adopt a responsible approach".

Should the talks collapse, it could carry the risk of Tehran getting to within a short sprint of nuclear weapons and igniting a fresh war in the Middle East. It could also prompt the West to impose more harsh sanctions on Iran and further escalate world oil prices already strained by the Ukraine conflict.

European negotiators from France, Britain, and Germany had already temporarily left the talks as they believed they had gone as far as they could go and it was now up to the two main protagonists to agree on outstanding issues, including the extent to which sanctions on Iran would be rolled back.

Iran's Islamic Revolutionary Guard Corps, which is under U.S. sanctions, successfully put a second military satellite into orbit, state media said on Tuesday, in what would be another advance for Iran's military.