The Russian government is linking a brewing effort to revive the 2015 Iran nuclear deal with ongoing international sanctions against the Kremlin over its invasion of Ukraine -- potentially casting the cautious talks into doubt.

Russian Foreign Minister Sergey Lavrov said the Russians want promises that the sanctions being imposed on Moscow for its invasion will not affect its trading relationship with the Iranian regime.

AGREEMENT TO RESTORE IRAN NUCLEAR DEAL EXPECTED WITHIN DAYS: EUROPEAN DIPLOMAT

"We need guarantees these sanctions will in no way affect the trading, economic and investment relations contained in the (deal) for the Iranian nuclear program," Lavrov said.

"We have asked for a written guarantee…that the current process triggered by the United States does not in any way damage our right to free and full trade, economic and investment cooperation and military-technical cooperation with the Islamic State," he said according to The Wall Street Journal.

Talks have been ongoing in Vienna for weeks as part of the effort to bring the U.S. and Iran back into the 2015 Joint Comprehensive Plan of Action (JCPOA.) A European diplomat told Fox News on Friday that a new deal is expected within days.

However, the diplomat noted that any deal that involves countries like Iran, Russia, China and the U.S. could always unravel -- while on Saturday a Western diplomat told the Journal that such a demand from Russia could throw the deal into doubt.

The JCPOA set limits on Iran’s nuclear activity in exchange for a significant rollback of international sanctions. The Trump administration pulled the U.S. out of the deal amid concerns that the agreement did not do enough to curb Iran’s nuclear ambitions -- including the sunset clauses on restrictions.

IRAN NEARING NUCLEAR THRESHOLD, WITH US OPTIONS TO STOP IT NARROWING, REPORT WARNS 

Iran eventually pulled out of the deal after the Trump administration re-imposed sanctions as part of its maximum pressure campaign, and Tehran has been ramping up its enrichment since then. 

The International Atomic Energy Agency (IAEA) said this week it believes Iran has significantly increased its stockpile of highly enriched uranium, but that it is unable to verify the exact size of the stockpile due to limits imposed on inspectors by the regime.

Iranian officials on Saturday suggested that it had reached an agreement to provide documents to the IAEA about its program after the agency’s chief has visited Tehran to help close the deal.

"It would be difficult to believe or to imagine that such an important return to such a comprehensive agreement like the [JCPOA] would be possible if the agency and Iran would not be seeing eye to eye on how to resolve these important safeguards issues," the IAEA’s Rafael Mariano Grossi said in Tehran.

CLICK HERE TO GET THE FOX NEWS APP

With Russia’s involvement in the deal, it raises the possibility of financial benefit for Moscow in a new deal, like payments to take Iranian uranium. The diplomat who spoke to Fox News on Friday said that the West will find a way to enable the deal, and says the concerns are "nothing that can’t be overcome."

Fox News’ Rich Edson and The Associated Press contributed to this report.