A Russian diplomat taking part in renewed talks with Iran said Tehran got much more than anyone expected as it negotiated with other nations to revive the 2015 nuclear deal.

"Iranian colleagues are fighting for [their] national interest like lions," Russian diplomat Mikhail Ulyanov said in a video interview posted online by Polaris NatSec. "They fight for every comma, every word, and as a rule, quite successfully."

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

A nuclear agreement involving the United States, China, Russia and Iran is expected within days, officials previously told Fox News. The talks have been mired in uncertainty after Russia made last-minute demands that assure guarantees that the sanctions it faces over its invasion of Ukraine will not hurt trade with Iran. 

The 2015 Joint Comprehensive Plan of Action (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 pulled out of the deal after the Trump administration imposed sanctions. 

In the video, Ulyanov praised the Chinese over their role in the negotiations and said they worked well with Russia during the talks. 

"I am absolutely sincere in this regard when I say that Iran got much more than it could expect," he said. "Our Chinese friends were also very efficient and useful as co-negotiators."

"I can recollect dozens of such cases when on rather serious, significant questions, we managed together to get positive results close to what we wanted to achieve," he added. 

The Biden administration has sought to revive the nuclear deal, but talks stalled after Iranian leaders demanded a significant reduction in sanctions. 

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Over the weekend, Secretary of State Antony Blinken said sanctions on Russia over its Ukraine invasion were not related to the potential nuclear deal with Iran. 

"These things are totally different and just are not, in any way, linked together. So I think that's irrelevant," Blinken said in an interview with CBS's "Face the Nation."

Fox News' Rich Edson and Adam Shaw contributed to this report.