The UN's nuclear watchdog in Vienna reported that Iran has started producing uranium metal in defiance of the landmark 2015 accord, which former US president Donald Trump backed out of in 2018.

The move came as Iran warned that time was running out for President Joe Biden's administration to save the agreement from collapse.

Iran's ally Russia expressed sympathy for Tehran's position, while nonetheless urging against provocations.

"We understand the logic of their actions and the reasons prompting Iran. Despite this it is necessary to show restraint and a responsible approach," Russia's deputy foreign minister Sergei Ryabkov told state news agency RIA Novosti.

France also warned Iran against any further escalation of its row with the West, which it hopes Biden will help resolve.

The French foreign ministry said there was a need to "preserve the political space for a negotiated solution" to the standoff.

"In this context we call on Iran to not take any new measure that would further aggravate the situation on the nuclear front, which is already extremely concerning due to the accumulation of Iranian violations of the Vienna accord," the ministry added.

But Iran's Foreign Minister Mohammad Javad Zarif reiterated Tehran's stance that Washington must take the first step toward restoring the deal, known as the Joint Comprehensive Plan of Action.

"Biden administration officials keep talking about Iran's compliance with JCPOA -- In what capacity?" Zarif said on Twitter.

"U.S. ceased participation in May 2018, violated JCPOA & punished those complying with UN resolution. As of today, US remains in EXACTLY same position. Before spouting off, COMPLY," he wrote.

The deal reached by Iran with the US, China, Russia, Germany, France and Britain, which aims to prevent Iran developing an atomic bomb, bans Tehran from "producing or acquiring plutonium or uranium metals or their alloys" for 15 years.

Trump dramatically withdrew from the nuclear deal as part of a campaign of "maximum pressure" on Iran, which included the reimposition of crippling economic sanctions.

Biden is seeking to revive the agreement, but the two sides appear to be in a standoff over who should act first.

Iran denies having any ambitions of building a nuclear bomb, but said last month it was researching the production of uranium metal, a potential component for nuclear weapons.

The Vienna-based International Atomic Energy Agency (IAEA) said Wednesday that it had verified the production of 3.6 grammes of uranium metal at a plant in Iran.

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