They said the meeting to address Iran's compliance with the Joint Comprehensive Plan of Action, or JCPOA as the deal is formally known, needed to be "convened urgently," but they did not say when that would happen.
"Iran has stated that it wants to remain within the JCPOA," the countries said in a statement. "It must act accordingly by reversing these activities and returning to full JCPOA compliance without delay."
Europe is under pressure from the U.S. to abandon the accord entirely, as Washington did unilaterally last year, and it also is being squeezed by Iran to offset the ever-crippling effects of American economic sanctions.
That has left the Europeans' soft-power approach strained to its limits at a time of increasing tensions in the Middle East.
"For the Europeans, it's going to be difficult not to lose credibility in their position with Iran and also with Washington, by not being too soft, but at the same time acknowledging that there is some truth to what Iran is saying," said Adnan Tabatabai, a political scientist with the Bonn-based CARPO think tank on Middle Eastern affairs.
They are forced to walk a fine line, trying not to escalate the situation on either side as they seek a resolution between Tehran and Washington, with French President Emmanuel Macron taking the lead for the three European countries, known as the E3, said Sanam Vakil, a researcher with London-based Chatham House think tank.
"What the E3 can do is kick-start diplomacy and diplomatic conversations," she said. "They can potentially convince Iran to freeze its breach and prevent any further breaches, while shepherding a process back and forth between Washington and Iran — worst case scenario is that nothing happens, but at least they've bought themselves time."
So far, neither Iran's announcement last week that it had exceeded the amount of low-enriched uranium allowed under the deal, nor Monday's revelation it had begun enriching uranium past the 3.67% purity allowed, to 4.5%, are seen as such gross violations that they are likely to prompt Europe to invoke the deal's dispute resolution mechanism. Both of Iran's actions have been verified by the U.N.'s nuclear watchdog, the International Atomic Energy Agency.
That mechanism is a month-long process, which could lead to the matter being brought before the U.N. Security Council and could result in the eventual "snapback" of sanctions that had been lifted under the deal.
"Iran's actions are still within the framework of calibrated escalation," Tabatabi said. "It gives some room for maneuver, and I would expect the Europeans to use this room over the next five or six weeks."
Experts warn that higher enrichment and a growing stockpile narrow the one-year window Iran would need to have enough material for an atomic bomb, something Iran denies it wants but the deal prevented.
Macron talked directly about the issue on Saturday with Iranian President Hassan Rouhani, and separately Monday with President Donald Trump.
Macron sent his top diplomatic adviser, Emmanuel Bonne, to Tehran where he was expected to meet Wednesday with the country's senior security official, Ali Shamkhani, according to Iran's semi-official Tasnim news agency. Bonne hopes to try to "obtain gestures" from Iran to show they're serious about staying in the deal, a French official said.
"The idea is to privilege dialogue (over) escalation that can become explosive," and "not reach a situation of war," said the official, who was not authorized to speak publicly on the matter so asked for anonymity.
This is the second trip to Tehran by Bonne, who was there in mid-June for one day.
"This is very much an E3 process, but Macron is leading it because obviously the U.K. is in a period of leadership transition and Germany is taking a slightly less-visible role, but I think there is great unity here," Vakil said.
The U.S. has sent thousands of troops, an aircraft carrier, nuclear-capable B-52 bombers and advanced fighter jets to the Middle East, and fears are growing of a wider conflict after mysterious oil tanker attacks near the Strait of Hormuz blamed on Iran, attacks by Iranian-backed rebels in Yemen on Saudi Arabia, and Iran's downing of a U.S. military drone.
In a thinly veiled threat to Iran on Tuesday, Israeli Prime Minister Benjamin Netanyahu stood in front of an F-35 stealth fighter during a tour of an air base and said one should "remember that these planes can reach every place in the Middle East, including Iran and certainly Syria."
Britain, France and Germany urged "all parties to act responsibility toward deescalating ongoing tensions regarding Iran's nuclear activities," in their joint statement. They did not mention any country by name other than Iran itself.
Trump pulled the U.S. out of the deal last year, saying he wanted to negotiate a better one. Under the provisions of the accord, signatories provided Iran with economic relief in exchange for curbs on the country's nuclear program, but the latest U.S. sanctions have highlighted the inability of the Europeans, as well as Russia and China, to keep up with their commitments.
Iran's recent moves — which it defends as permissible after the U.S. withdrawal — are seen as a way to force the others to openly confront the sanctions.
Speaking to the French Senate, Foreign Minister Jean-Yves Le Drian said Iran had made "a bad reaction to a bad decision," referring to the U.S. withdrawal. He said Macron was trying to create a "space for dialogue."
"The Americans, even if they're no longer signatories ... can make needed gestures of appeasement to open a space of discussion to avoid an uncontrolled escalation, or even an accident," he said.
China and Russia both expressed regret at Iran's moves but suggested the U.S. had pushed Iran into a corner.
Iran had given the Europeans a 60-day warning it would increase the purity of its enrichment, but they were unable to come through with the economic relief being sought by Tehran by the deadline. Iran has set a new 60-day deadline, saying it would "resume the reduction of our commitments" in the nuclear deal. That deadline is Sept. 5, although a senior Iranian vice president described it as being Sept. 7.
One Iranian official hinted in a state TV interview broadcast Monday that Iran might consider going to 20% enrichment or higher if material needed and the country still hasn't gotten what it wants from Europe. That would worry nuclear nonproliferation experts because 20% is a short technical step away from reaching weapons-grade levels of 90%.
The IAEA board of governors plans to convene Wednesday in Vienna at the request of U.S. to discuss the recent developments.
Associated Press writers Elaine Ganley in Paris and Nasser Karimi in Tehran contributed.