By Rory Jones 

DUBAI -- Iranian ships attempted to impede the passage of a U.K.-flagged commercial vessel through the Persian Gulf, the British Defense Ministry said, a move that threatens to escalate already high tensions in the region.

Three Iranian vessels tried to block the BP PLC-run tanker British Heritage in the Strait of Hormuz on Wednesday but turned away after the U.K. warship trained its guns on the vessels, according to the ministry.

The incident is likely to further spook international shipping markets and investors and could accelerate U.S. moves to build a coalition of states to protect commercial vessels near Iranian waters, after a series of attacks on ships in recent months.

Front-month West Texas Intermediate futures recently were up 0.6% to $60.81, while Brent futures were 0.8% higher at $67.51.

The U.S. and U.K. have accused Iran of mounting assaults on vessels but this is the first time since tensions flared earlier this year that a Western warship has come close to military engagement with Iranian naval forces.

The British Royal Navy frigate, HMS Montrose, issued verbal warnings to the Iranian ships before they backed away, the ministry said Thursday.

"We are concerned by this action and continue to urge the Iranian authorities to de-escalate the situation in the region," it said, adding that the attempt to block the British Heritage's passage contravened international law.

A spokesman for the ministry added that the British Heritage had since left the Persian Gulf but didn't identify the types of Iranian vessels involved.

Britain has maintained a naval presence in the region for some time. HMS Montrose has been in the Persian Gulf since late 2018 and the country currently has four minesweepers deployed there.

A spokeswoman for the British Ministry of Defense wouldn't comment if the government planned to increase its naval presence in the Gulf.

Sepahnews.com, an Iranian news website tied to the Islamic Revolutionary Guard Corps, denied the unit's forces had tried to detain the ship. "During the past 24 hours, no encounter has been made with foreign vessels including British vessels," the Revolutionary Guard said, according to Sepahnews.com.

Iranian officials have threatened to seize a British ship in the Persian Gulf after U.K. special forces last week commandeered an Iranian ship off the coast of Gibraltar. That ship was carrying oil bound for Syria in what U.K. officials said breached European Union sanctions on sales of oil to the country. Tehran has denied that the tanker was headed to Syria and called its seizure illegal because Iran isn't subject to a European oil embargo.

Iranian President Hassan Rouhani on Wednesday, warned the U.K., according to Iran's Press TV. "You are the ones initiating insecurity, and will come to realize its consequences in the future."

BP said Thursday, "our top priority is the safety and security of our crews and vessels. While we are not commenting on these events, we thank the Royal Navy for their support."

The British Heritage had been on its way to pick up a cargo of oil from Basrah port in southern Iraq when it changed course earlier this week, without loading, after the Iranian threats.

BP is a partner in the development of Iraq's Rumaila, the world's third largest producing field, and it shipped around 50,000 barrels a day of Iraqi oil in 2018, via the Strait of Hormuz.

"We've just got to be really careful about our ships," BP Chief Executive Bob Dudley said at an event at London-based think tank Chatham House on Wednesday, in relation to Iran's threats.

Iran's threats in the Persian Gulf have added another layer to the situation unfolding around Tehran's breaches of limits of the 2015 nuclear agreement, from which the Trump administration withdrew last year.

The U.S. also has accused Iran of attacking tankers in the Gulf of Oman -- which Tehran denied -- and said Iran shot down a U.S. spy drone in the area. Tehran said the unmanned aerial vehicle was inside Iranian airspace when it was downed.

The U.K. has backed the U.S. assertion that Iran attacked the ships. But London has been at odds with the White House over its decision to pull out of the nuclear deal, and British officials are working with European nations on how to salvage the accord.

The attacks on tankers have roiled oil markets and increased the costs of transporting crude and other products in and out of the Persian Gulf. Roughly one third of the world's seaborne crude moves through the Strait of Hormuz from countries such as Iraq, Saudi Arabia and the United Arab Emirates.

BP on Monday halted the British Heritage's passage through the Persian Gulf over fears it would be seized by Iranian forces. The tanker was sailing toward Iraq's Basra oil terminal when it turned around on Saturday and stopped off the coast of Saudi Arabia. The ship was located off the coast of Oman early Thursday morning, according to MarineTraffic.com.

The U.S. has worked in recent weeks on a plan for deterring attacks on tankers that calls for ships from Arab, Asian and other foreign nations to stand watch in the Persian Gulf and the Gulf of Oman while maritime patrol planes fly overhead.

Saudi Arabia and the U.A.E., which export a large amount of oil through the Strait of Hormuz, have backed such a plan.

"This idea has to be thought out," said Abdulkhaleq Abdulla, a political scientist and former professor in the U.A.E. "Gulf states would be happy to see this internationalization of Gulf security."

Military analysts say the threat is clear. The Revolutionary Guard Corps is equipped to swarm hostile vessels with fast boats armed with torpedoes and short-range missiles and small patrol craft equipped with machine guns and rocket launchers.

Military escorts in the region have a precedent. During the Iran-Iraq war in the 1980s, the two countries attacked each other's ships in the Gulf and Iran eventually began targeting foreign-flagged vessels. The assaults subsided when the U.S. escorted and reflagged foreign tankers under its ensign.

--Aresu Eqbali in Tehran contributed to this article.

Write to Rory Jones at rory.jones@wsj.com

 

(END) Dow Jones Newswires

July 11, 2019 04:59 ET (08:59 GMT)

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