"We all agreed the urgent need for de-escalation. Iran cannot have a nuclear bomb, and diplomacy is the solution to prevent this, and (the) EU will play its part," EU foreign policy chief Kaja Kallas said following a video call.

Europe has been left largely on the sidelines in efforts to curb the violence between the two Middle East foes after Israel unleashed its initial strikes on Iran.

Europe played a key role in negotiating and overseeing a 2015 agreement on Iran's nuclear programme that Trump tore up during his first term in office.

Trump's administration had been trying to agree a new deal with Tehran before Israel kicked off the latest strikes, and talks are now on hold.

"As the Iran and US talks have run into some kind of standstill", Europe "has more to say", Kallas said, adding that she had spoken Monday to Iran's foreign minister and key European counterparts.

Kallas said European countries were coordinating efforts to evacuate citizens who wanted to leave the region.

"We have member states that have planes leaving, we have member states who don't have planes, and we coordinate the efforts so that our citizens are safe," she said.

The EU's top diplomat said she had received reassurances from US counterpart Marco Rubio that Washington was not looking to join in Israel's attacks on Iran.

"This is in nobody's interest," she said.