“This is the first time that the E.U. has done something so public and so aggressive. I imagine it was also coordinated in some manner with the U.S. given that NATO member forces have been involved.”

Iran condemned the United Kingdom on Friday for seizing an Iranian oil tanker on suspicion it was carrying oil to the Syrian government in violation of E.U. sanctions.

Iran’s foreign ministry demanded an immediate return of the oil tanker and a senior Islamic Revolutionary Guards Corps (IRGC) commander threatened to seize a British tanker in retaliation.

“If Britain does not release the Iranian oil tanker, it is the authorities’ duty to seize a British oil tanker,” said Mohsen Rezai, a senior IRGC commander.

Iranian foreign ministry spokesman Abbas Mousavi said “the move indicated that the U.K. follows the hostile policies of the U.S., which is unacceptable for the Iranian nation and government” and said the U.K.’s ambassador to Tehran had been summoned over the “form of piracy.”

Worsening US-Iran Relations

The news comes amid spiking military tensions between the U.S. and Iran. Iranian President Hassan Rouhani pledged to increase Iran’s uranium enrichment to “any amount we want” on Wednesday, prompting concern from European leaders trying to salvage the nuclear deal. When asked about Iran’s uranium plans on Monday, President Trump told reporters, “They know what they’re playing with, and I think they’re playing with fire.”

“Rouhani says that they will Enrich Uranium to ‘any amount we want’ if there is no new Nuclear Deal. Be careful with the threats, Iran. They can come back to bite you like nobody has been bitten before!” the president tweeted late Wednesday.

In a statement, the U.K.’s foreign office supported the tank seizure: “We welcome this firm action by the Gibraltarian authorities, acting to enforce the E.U. Syria Sanctions regime.”

Spanish Foreign Minister Josep Borrell said the Iranian tanker was seized after a U.S. request.

James Robbins, BBC’s diplomatic correspondent, argued the U.K. would not have acted to enforce U.S. sanctions on Iran, but was instead acting to prevent oil from reaching Syria. The tanker took a suspiciously long voyage along the southern coast of Africa that Robbins believes was an Iranian attempt to conceal its destination in Syria.

U.S. National Security Adviser John Bolton, who reportedly was a driving force behind airstrikes on Iran that Trump canceled last month, was excited by the tank seizure:

“Excellent news: U.K. has detained the supertanker Grace I laden with Iranian oil bound for Syria in violation of E.U. sanctions,” Bolton tweeted. “America & our allies will continue to prevent regimes in Tehran & Damascus from profiting off this illicit trade.”

Al Jazeera’s Dorsa Jabbari, reporting from Tehran, said the Iranian regime viewed its actions as legal under international law.

“They don’t recognize the E.U. sanctions on the Syrian government as legitimate because they have not been endorsed by the United Nations,” said Jabbari. “They say that this act by the British government on behalf of Americans is tantamount to piracy.”

While Bashar al-Assad’s brutal treatment of the Syrian people has prompted severe sanctions from the European Union, the Iranian regime views the tank seizure as a gesture of Western imperialism and economic warfare rather than a genuine act for the human rights of Syria’s people.

In 1953, the U.S. and U.K. worked together to overthrow the democratically-elected prime minister of Iran, Muhammad Mossadegh, because the leader nationalized his country’s oil against the interest of Western firms. Backlash against the Shah, the Western-backed implanted leader who was heavily armed by the United States, culminated in the 1979 Iranian revolution and the Ayatollah’s Islamic regime. The U.S. and Iran have held hostile relations ever since.

According to Al Jazeera, Iran exported more than 2.5 million barrels of crude per day in April 2018, a month before the Trump administration pulled out of the nuclear deal. In late June, Iran only exported 300,000 barrels per day, a consequence of Washington’s sanctions on Iran’s most crucial export.

Europe’s Relationship With Iran Stressed Over Tanker Seizure

“This is the first time that the E.U. has done something so public and so aggressive. I imagine it was also coordinated in some manner with the U.S. given that NATO member forces have been involved,” Matthew Oresman told Al Jazeera.

The move will complicate Iran’s relations with European countries that have been striving to save the nuclear deal and alleviate tensions in the Gulf.

While some European countries have demanded more evidence before accusing Iran of attacking oil tankers in the Gulf of Oman last month, the U.K. supports the official U.S. position blaming Iran. Beyond foreign policy, U.K.-Iranian relations have also been strained by the jailing of British dual nationals.

“This is likely to have been meant as a signal to Syria and Iran – as well as the U.S. – that Europe takes sanctions enforcement seriously and that the E.U. can also respond to Iranian brinkmanship related to ongoing nuclear negotiations,” said Oresman.