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Months-long talks with Iran to revive the 2015 nuclear deal hit a snag Friday after Russia demanded sanctions imposed on Moscow for its war in Ukraine be excluded from Tehran dealings.  

A source with knowledge of the discussions told Fox News that the Russian delegation upended final-hour negotiations by demanding sanction immunity for any future trade with Iran.

President Hassan Rouhani, second right, listens to the head of the Atomic Energy Organization of Iran, Ali Akbar Salehi, while visiting an exhibition of Iran's new nuclear achievements in Tehran, Iran, in April.

President Hassan Rouhani, second right, listens to the head of the Atomic Energy Organization of Iran, Ali Akbar Salehi, while visiting an exhibition of Iran's new nuclear achievements in Tehran, Iran, in April. (Iranian Presidency Office/AP)

President Biden made it a top priority of his administration to reinstate the Joint Comprehensive Plan of Action (JCPOA) after the U.S. abandoned the plan under former President Trump in 2018.

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JCPOA member nations like the U.K., France, Germany and the EU warned against the move and urged Iran to continue its existing commitments to the deal. 

But by 2019 Tehran argued the deal was moot due to crippling sanctions imposed by the U.S. and began redeveloping its nuclear program.

JCPOA member nations, including top U.S. adversaries like China and Russia, backed the administration’s push to re-establish the nuclear deal last year. 

But nuclear talks with Tehran have proven to be slow, and White House officials have repeatedly warned Iranian counterparts that time is running out to find a solution.

President Biden gives remarks at an event in the East Room of the White House on Feb. 28, 2022, in Washington, D.C.

President Biden gives remarks at an event in the East Room of the White House on Feb. 28, 2022, in Washington, D.C.  (Anna Moneymaker/Getty Images)

The U.S. announced it was negotiating with Iran through indirect talks in March 2020, but by June the efforts were stonewalled following the election of anti-Western President Ebrahim Raisi.

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Talks eventually resumed, but questions over good-faith negotiations prompted several halts in the months-long discussions.

The White House said this week that it was "close" to wrapping up a deal.

"We have been close for some time now," White House press secretary Jen Psaki said. "The end of negotiations is always when the difficult and challenging parts of the conversation typically take place."

But deteriorating ties with Moscow over Russian President Vladimir Putin’s war in Ukraine with the West has prompted new hurdles for Washington and its allies. 

On Tuesday, Secretary of State Antony Blinken told Fox News that Russia was continuing to participate in the negotiations and said, "We continue to work to see if we can come back to mutual compliance with Iran on the deal." 

"Russia continues to be engaged in those efforts, and it has its own interests in ensuring that Iran is not able to acquire a nuclear weapon," he added.

But new demands from Moscow appear to have once again stunted talks.

High Representative of the EU for Foreign Affairs and Security Policy Josep Borrell Fontelles took to Twitter to say that a final text was "essentially ready and on the table" and vowed to continue working to reach an agreement. 

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But apart from Russia’s attempts to circumvent its own crippling sanctions, sources have told Fox News that Iran is seeking additional demands of its own.

Iran has now called on the White House to remove its military branch, the Islamic Revolutionary Guard Corps, from the Foreign Terrorist Organizations list – a step that Biden has been unwilling to take, Fox News is told. 

Fox News' James Levinson and Gillian Turner contributed to this report.