Portuguese Foreign Minister Augusto Santos Silva (L) with Spanish Foreign Minister Josep Borrell (C) and EU's High Representative for Foreign Affairs and Security Policy Federica Mogherini during a EU Foreign Affairs Council meeting at the EU headquarters in Brussels on May 13, 2019 | Jophn Thys/AFP via Getty Images EU tells Pompeo to cool tensions with Iran ‘Accidents happen when tension is rising,’ Greece’s top diplomat says.

Top European Union officials told U.S. Secretary of State Mike Pompeo on Monday to exercise "maximum restraint" in Washington's standoff with Tehran.

EU foreign policy chief Federica Mogherini and foreign ministers from leading EU countries delivered the message at a series of meetings after Pompeo made an unexpected visit to Brussels. Several ministers expressed fears that tension between the United States and Tehran could flare into a military conflict.

Pompeo “heard very clearly today from us, not only from myself but also from the other ministers of EU members states, that we are living in a crucial, delicate moment where … the most responsible attitude to take … should be that of maximum restraint, avoiding any escalation on the military side,” Mogherini told reporters.

At a regular gathering in the Belgian capital, EU ministers did not hide their fears that U.S. strategy toward Tehran carries grave risks.

“I think there's a real concern that an escalation that is unintended could end up with a much more serious situation than we're fearing," British Foreign Secretary Jeremy Hunt told reporters ahead of the meeting.

On the sidelines of the meeting, Hunt and Mogherini also held talks with the foreign ministers of Germany and France, the other two European signatories of the 2015 deal that lifted sanctions on Tehran in return for a suspension of Iran's nuclear program. Pompeo also met with Mogherini and with the ministers of the three EU countries that signed the deal.

The deal, formally known as the Joint Comprehensive Plan of Action (JCPOA), was backed by the Obama administration but U.S. President Donald Trump branded the pact “a disaster” and pulled out last year.

Last week Iran decided to withdraw from some parts of the deal and gave a 60-day ultimatum to the signatories to deliver on their promises to protect Iran's oil and banking sectors from U.S. sanctions. The EU rejected that ultimatum immediately but declared it still wants to preserve the deal.

The U.S reacted with new sanctions, on top of those already imposed on oil exports, and has been increasing air and naval power in the Middle East in recent weeks.

But senior EU officials called for the bloc to remain committed to the pact.

“It is important that Europe stays united regarding this issue. It has been the case so far and I am convinced that it will remain so,” French Foreign Minister Jean-Yves Le Drian told reporters.

Some countries, like France, argue the current deal could be improved by being amended to try to curb Iran's ballistic missiles program, for example.

German Foreign Minister Heiko Maas said he had made clear to Pompeo that Berlin is sticking to the deal and is worried by the rise in tension.

“I was again clear about our concerns in view of tension in the region. We want to prevent a military escalation and the nuclear deal with Iran is the foundation for that, that Iran does not acquire any nuclear weapons and that we maintain this deal,” he told reporters.

Pompeo did not speak to journalists at the EU building that was the venue for Monday's meetings, but Brian Hook, the U.S. special representative for Iran, defended the U.S. approach to reporters, arguing that it was the best way to get Tehran to change its behavior.

“If talking nicely worked, we would have settled this decades ago, but this is a regime that only understands economic pressure and diplomatic isolation,” Hook said. “We are committed to this strategy because it has the best chances of de-escalating the threats.”

He argued that historically, the only way Iran has changed its behavior was when there were certain elements present: “Economic pressure, diplomatic isolation and the threat of military force. It’s always one or more of those elements that have to be present.”

The announcement of Pompeo's arrival in Belgium came as a surprise on Sunday evening when the State Department said he canceled a planned visit to Moscow to head to Brussels instead. Hook said Pompeo felt it was necessary to share with his allies “information and intelligence” on the situation in Iran amid the “escalating” threats.

Pompeo’s visit came as Saudi Arabia alleged that two of its oil tankers had been victims of “sabotage” off the coast of the United Arab Emirates. An oil tanker flying the UAE flag and one flying the Norwegian flag also were targeted, according to media reports. Details about the alleged sabotage were unclear, though CNN reported that it had captured images of damage to the hull of the Norway-flagged vessel.

Although there were no direct accusations that Iran was behind the suspected sabotage, the rising tension between Washington and Tehran has spurred concerns that Iran or proxy groups allied with it might aim to disrupt the global oil supply. Iranian officials, however, expressed concern about the latest reports, while also warning against foreign “adventurism” in the region.

Europeans' concerns about a possible war with Iran stem in part from the hawkish stance of U.S. National Security Adviser John Bolton. Diplomats point to an op-ed Bolton wrote in 2015 — before he took up his current post — entitled “To Stop Iran’s Bomb, Bomb Iran.”

“I don't think that anybody wants a war in Iran or generally in the Middle East, but accidents happen when tension is rising so we must be very careful,” Greek Foreign Minister George Katrougalos told POLITICO in an interview.

Yet officials also admit that the EU is toothless when it comes to its ability to counter aggressive U.S. foreign policy.

The EU has set up a so-called special purpose vehicle intended to let European companies continue to trade with Iran. But European firms could face heavy penalties from the U.S. if they choose to take that path.

"A lot depends on the willingness of companies," Johannes Hahn, the European commissioner for relations with the bloc's neighbors, told reporters. "We have created the conditions for European companies to do business with Iran, but nevertheless many companies are concerned that if they do business with Iran, there will be consequences for their activities in the United States, that’s why they are holding back."

“I cannot force a private company to do business in Iran,” he added.

Katrougalos said the dispute over Iran underscored a need for the EU to strengthen its own foreign and defense policy.

“Sometimes it looks that we don't have our policy and we're drowned behind the other great powers," he said.

Nahal Toosi contributed reporting from Washington.

This article has been updated.