The leaders of Germany, France, the United Kingdom and the United States expressed their "grave and growing concern" about Iran's nuclear programme after meeting on the sidelines of the Group of 20 summit in Rome.
The four leaders said Iran "has accelerated the pace of provocative nuclear steps, such as the production of highly enriched uranium and enriched uranium metal."
"Iran has no credible civilian need for either measure, but both are important to nuclear weapons programs," they noted.
The leaders said the situation underscored the importance of Iran and the United States coming back to the 2015 nuclear deal known as the Joint Comprehensive Plan of Action.
Former US President Donald Trump withdrew from the deal, which imposed limits on Iran's nuclear enrichment programme, in 2018. Britain, France, Germany, Russia, China and the European Union remain part of the deal.
France's Emmanuel Macron, Britain's Boris Johnson, Germany's Angela Merkel and the US' Joe Biden said they believed it was "remains possible to quickly reach and implement an understanding on return to full compliance to ensure for the long term that Iran’s nuclear program is exclusively for peaceful purposes, and to provide sanctions lifting with long lasting implications for Iran’s economic growth."
They called on Iranian President Ebrahim Raisi to avoid a "dangerous escalation" of the situation.
The UN's nuclear watchdog, the International Atomic Energy Agency, has said they are concerned that nuclear material is present at undeclared locations in Iran.
While talks to bring Washington and Tehran back into compliance have been on hiatus since June, when Iranian President Raisi took power, Iran recently said the country had agreed to restart negotiations.
The meeting comes days after US officials blamed Iran for resourcing a drone attack on a US outpost in Syria. No deaths or injuries were reported as a result of the attack.
In retaliation, the U.S. Treasury Department on Monday announced new penalties against two senior members of Iran’s Revolutionary Guard Corps and two affiliated companies for supplying lethal drones and related material to insurgent groups in Iraq, Lebanon, Yemen and Ethiopia.
This story has been updated with the statement from the leaders.