DUBAI (Reuters) - An Iranian tanker at the centre of an angry confrontation between Iran and Washington sailed for Greece on Monday after it was freed from detention off Gibraltar, as Washington called the release unfortunate and warned Greece and Mediterranean ports against helping the vessel.

Tehran said any U.S. move to seize the vessel again would have “heavy consequences”. While Iranian Foreign Minister Mohammad Javad Zarif appeared to downplay the possibility of military conflict with Washington in an interview on U.S. television, he also indicated on a visit to Finland that Washington was seeking “more escalation”.

The Grace 1, renamed the Adrian Darya 1, left anchorage off Gibraltar about 11 p.m. (2100 GMT) on Sunday. Refinitiv ship tracking data showed on Monday that the vessel was heading to Kalamata in Greece and was scheduled to arrive next Sunday at 0000 GMT.

The seizure of the tanker by British Royal Marines near Gibraltar in July 4 on suspicion of carrying oil to Syria in violation of European Union sanctions led to a weeks-long confrontation between Tehran and the West. It also heightened tensions on international oil shipping routes through the Gulf.

Gibraltar, a British overseas territory, lifted the detention order on Thursday. But the next day, a federal court in Washington issued a warrant for the seizure of the tanker, the oil it carries and nearly $1 million.

Gibraltar said on Sunday it could not comply with that request because it was bound by EU law. Washington wanted to detain the tanker on the grounds that it had links to Iran’s Islamic Revolutionary Guard Corps (IRGC), which it has designated a terrorist organisation.

‘UNFORTUNATE’

“It’s unfortunate that that happened,” U.S. Secretary of State Mike Pompeo told Fox News Channel about the ship’s release.

Pompeo said that if Iran was successful in making a profit from the tanker’s oil cargo, IRGC elite forces would have “more money, more wealth, more resources to continue their terror campaign.”.

A U.S. State Department official said Washington had conveyed its “strong position” to the Greek government, as well as to all ports in the Mediterranean about facilitating the tanker.

The official said assisting the ship could be considered providing support to a terrorist organisation.

Zarif said in Finland: “We are happy this ordeal has ended and I hope this will lead to less escalation.”

He also said the U.S. warrant had no legal basis and was politically motivated to “make more escalation.”

But in an interview with “NBC Nightly News,” Zarif said Iran would not take military action to end its standoff with its longtime adversary.

“We will not. We have never done that, in the past 250 years. We have defended ourselves. And we have taught good lessons to those who invaded us,” Zarif said.

He also appeared to downplay the possibility of U.S. military action against the Islamic Republic in the interview, saying the U.S. habit of saying: “No option is off the table” in its approach to Iran was a violation of the U.N. Charter.

Greek authorities had no immediate comment on the situation.

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WARNINGS THROUGH OFFICIAL CHANNELS

Asked whether the United States could renew its seizure request after the tanker sailed from Gibraltar, Iranian Foreign Ministry spokesman Abbas Mousavi said: “Such an action, and even the talk of it ... would endanger shipping safety in open seas.”

“Iran has issued the necessary warnings through official channels, especially the Swiss embassy, to American officials not to commit such an error because it would have heavy consequences,” Mousavi said in remarks on state television.

Switzerland represents U.S. interests in Iran, which has no diplomatic relations with the United States.

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The Adrian Darya 1, which was reflagged to Iran after being delisted by Panama on May 29, was fully laden and carrying about 2 million barrels of oil, Refinitiv data showed. The cargo was valued at tens of millions of dollars.

U.S. President Donald Trump pulled out of a 2015 nuclear deal with Iran in May last year, while the European Union is still part of the accord, which allows Tehran to sell its oil.

Washington wants to reduce Iran’s oil exports to zero and has reimposed U.S. sanctions that place heavy penalties on any breaches even for non-U.S. citizens and companies, including asset freezes and being cut off from the U.S. financial system.

While EU regulations still allow for companies and citizens in the bloc to trade with Iran, falling foul of U.S. sanctions has meant most banks are unwilling to process even authorised transactions such as for food and medicine, finance sources say.

It is likely to be the first major foreign policy test for Greece’s new prime Minister, Kyriakos Mitsotakis, since he took office in July if the vessel enters Greek territorial waters.

Zarif said that because of U.S. sanctions, Iran could not disclose where the oil would go.

The Greek coastguard said it had no formal information the vessel was heading to Kalamata and was monitoring the matter.

TANKER HELD BY IRAN

Separately, a senior Iranian lawmaker said a crisis in Iran’s ties with Britain, which included Tehran’s seizure of a British-flagged tanker last month, would not be over until the tanker reached its destination.

Iran’s Revolutionary Guards on July 19 seized the Stena Impero in the Strait of Hormuz waterway for alleged marine violations, two weeks after the Grace 1 was commandeered.

“Until the Iranian oil tanker arrives at its destination the British must help end the crisis,” Heshmatollah Falahatpisheh, of parliament’s national security and foreign affairs committee, was quoted as saying by semi-official ISNA news agency.

“The crisis with Britain is not over. Britain has the primary responsibility for ending the oil tanker crisis,” Falahatpisheh said.

Mousavi said Tehran was waiting for a court decision on alleged maritime violations by the Stena Impero and he hoped the procedures would be completed as soon as possible.