"Negotiations on Iran's nuclear programme should restart as soon as possible" and "cooperation" with the International Atomic Energy Agency must resume, EU foreign policy chief Kaja Kallas wrote on X after a phone call with Iranian Foreign Minister Abbas Araghchi.

"The EU is ready to facilitate this."

Kallas further warned Tehran that "any threats to pull out of the non-proliferation treaty don't help to lower tensions."

The call came after Aragchi ruled out a out a quick resumption of talks with the United States and said Tehran will first need assurances it will not be attacked again.

The United States and Iran were holding nuclear talks when Israel hit Iranian nuclear sites and military infrastructure. The United States joined the assault by bombing three nuclear sites -- Fordo, Natanz and Isfahan -- on June 21.

The EU has long sought to play a mediation role with Iran.

The 27-nation bloc was a signatory -- and facilitator -- of a 2015 deal between Iran and international powers over Tehran's nuclear programme.

US President Donald Trump abandoned that deal in 2018.