Britain, France and Germany on Tuesday said they "deeply regret" Iran's decision to restrict site inspections by the UN's nuclear watchdog after a US refusal to lift existing sanctions.
The three European signatories to the 2015 nuclear deal with Iran said they were "united in underlining the dangerous nature of this decision".
They said it would significantly constrain the International Atomic Energy Agency's access to sites and information on safety.
Washington on Monday also condemned Tehran's decision to restrict IAEA access to sites.
"We urge Iran to stop and reverse all measures that reduce transparency and to ensure full and timely co-operation with the IAEA," the UK, France and Germany said.
They said it was their objective to preserve the 2015 deal, which lifted economic sanctions on Iran in exchange for agreements on limits to its nuclear programme.
The European signatories, who stuck with the deal after the US withdrew under former president Donald Trump in 2018, said they would "support ongoing diplomatic efforts for a negotiated solution allowing for the return of Iran and the US to full compliance".
US President Joe Biden has indicated willingness to revive the nuclear deal but insists that Iran first returns to all of its nuclear commitments.
The Biden administration has said it is willing to join EU-led talks with Iran in search of a compromise.
Iran said it was limiting inspections because Mr Trump's sanctions had not been lifted after Sunday talks in Tehran with IAEA director Rafael Grossi, which were meant to lay the foundations for political discussion.
"We take note of the conclusion of a temporary bilateral understanding between the IAEA and Iran, which preserves for up to three months the possibility of access to certain information," the UK, France and Britain said.
The changes to the IAEA's monitoring and inspection regime, which were ordered by Iran's conservative-dominated Parliament last year, are the latest retaliatory measures Iran has adopted in response to the US withdrawal.
The Iranian Parliament passed a law last December that demanded some inspections by the IAEA be suspended if the US did not lift sanctions by Sunday, which the government in Tehran said needed to happen for it to return to the 2015 deal.
Despite this, a last-minute deal that would allow the UN's atomic watchdog some access to Iran’s nuclear plants means a diplomatic solution to tension with Tehran remains alive, experts say.
