LONDON — European nations worked Monday to keep diplomatic efforts to curb the Israel-Iran war alive as the two countries traded strikes following the United States’ weekend attack on Iran’s nuclear program. Calls for Tehran to enter talks with Washington appeared to fall on deaf ears as it reached out to ally Russia for support.

The crisis topped the agenda for European Union foreign ministers meeting in Brussels, where diplomats agonized about the potential for Iranian retaliation to spark a wider war and global economic instability.

“The concerns of retaliation and this war escalating are huge,” said the bloc’s foreign policy chief, Kaja Kallas.

Kallas said any attempt by Iran to close the Strait of Hormuz, a key route for global shipping, would be “extremely dangerous and not good for anybody.”

Europe seeks more talks

Along with the EU, the “E3” of Britain, France and Germany have led efforts to find a diplomatic solution, holding a tense seven-hour meeting in Geneva on Friday with Iran’s Foreign Minister Abbas Araghchi. A day after those talks ended with a vague promise to “meet again in the future,” U.S. bombers struck three Iranian nuclear and military sites.

No further E3 talks with Iran are currently planned, a European diplomatic official said on condition of anonymity to discuss the negotiations.

Still, U.K. Foreign Secretary David Lammy urged Iran to meet the E3 again, and to open negotiations with the United States. Planned U.S.-Iran talks in Oman were scuttled after Israel began attacking Iran’s nuclear facilities on June 13. Iran has since ruled out negotiating while it is under attack.

“Take the off-ramp, dial this thing down and negotiate with the United States immediately and seriously,” said Lammy, who spoke to both Araghchi and U.S. Secretary of State Marco Rubio on Sunday.

German Foreign Minister Johann Wadephul said Europe had a role to play, but that “a real precondition for a settlement to the conflict is that Iran be ready to negotiate directly with the U.S.”

It was Moscow that Iran reached out to Monday, though, sending Araghchi to meet President Vladimir Putin at the Kremlin. Putin condemned the United States’ “unprovoked aggression” against Iran and said Russia would help the Iranian people.

Putin said he saw the visit as a chance to explore “how we can get out of today’s situation.” Kremlin spokesman Dmitry Peskov said Russia had offered to mediate.

European diplomatic efforts were complicated by a lack of foreknowledge of the Trump administration’s moves. Some countries had no advance notice of the strikes. Britain was notified, but only shortly before bombs fell.