The foreign ministers from the three European countries said Tuesday's report by the UN nuclear watchdog IAEA showing that Iran had raised its uranium enrichment to 60 percent of purity was a cause for "grave concern", while talks to save the 2015 deal remain at a standstill.

Under the accord, Iran had committed to keep enrichment to 3.67 percent, though it had stepped this up to 20 percent in January, before further boosting its capabilities to the current 60 percent.

The development of these new capacities are "key steps in the development of a nuclear weapon and Iran has no credible civilian need for either measure," the European foreign ministers said in a statement.

"Our concerns are deepened by the fact that Iran has significantly limited IAEA access," they added.

The 2015 deal known formally as the Joint Comprehensive Plan of Action, or JCPOA, gave Iran relief from sanctions in return for curbs on its nuclear programme.

The Islamic republic has gradually rowed back on its nuclear commitments since 2018, when then US president Donald Trump withdrew from the JCPOA deal and began imposing sanctions.

Trump's successor Joe Biden said he hopes to revive the agreement and indirect talks in Vienna, through European intermediaries, started in the Austrian capital in April.

But the talks broke up on June 20 without any discernible progress.

"While refusing to negotiate, Iran is instead establishing facts on the ground which make a return to the JCPOA more complicated," the European foreign ministers said.

"Iran must halt all activities in violation of the JCPOA without delay," they said, urging Iran to return to reengage with negotiations in Vienna "as soon as possible".

The EU said earlier this month that Iran is ready to resume talks under new President Ebrahim Raisi, and meetings could take place in Vienna from early September.