U.K. navy intervenes as Iran tries to stop British oil tanker from leaving Persian Gulf

The British navy intervened to stop Iran from blocking a commercial oil tanker leaving the Persian Gulf, heightening friction just as European nations scramble to salvage a landmark nuclear accord with the Islamic Republic.

The BP Plc-operated British Heritage, which can carry as much as 1 million barrels of oil, was attempting to pass through the Strait of Hormuz, a shipping chokepoint at the mouth of the world’s largest oil-producing region, when three Iranian vessels tried to impede it, according to a U.K. government statement. Iran denied the charge.

The incident marks an escalation in a row that started after U.K. forces seized a tanker off Gibraltar earlier this month that was suspected of carrying Iranian oil to Syria. Iran denied the vessel was heading to Syria and vowed to retaliate. Britain’s action opened up a wrangle that could drag on for months and complicate efforts to contain a brewing crisis over Iran’s compliance with a 2015 deal meant to prevent it from developing a nuclear weapon.

The Royal Navy’s HMS Montrose, which was escorting the tanker, “was forced to position herself between the Iranian vessels and British Heritage and issue verbal warnings to the Iranian vessels, which then turned away.” The incident took place in international waters, the Defense Ministry said.

“We are concerned by this action and continue to urge the Iranian authorities to de-escalate the situation in the region,” the statement said.

Iran’s Revolutionary Guard Corps denied trying to impede the British tanker but said its forces could act fast if ordered to do so. “If it receives an order to seize foreign ships, naval forces can act fast, with determination and without hesitation within the geographic scope of its mission,” the semi-official Fars news agency reported.

We are concerned by this action and continue to urge the Iranian authorities to de-escalate the situation in the region

Benchmark Brent crude was 37 cents higher at $67.38 a barrel in London trading at 11:12 a.m. local time. Oil has been rallying since the middle of last week as tensions surrounding Iran stoke concerns crude flows may be disrupted.

The British Heritage was able to pass safely through the Strait of Hormuz and was now sailing along the Omani coast, according to tanker tracking data compiled by Bloomberg.

Thursday’s developments spotlight, however, the mounting risks to shipping in a region that exports about a third of all seaborne petroleum. BP had been keeping the British Heritage empty inside the Gulf, near Saudi Arabia, rather than risk its seizure by Iran in a tit-for-tat retaliation, a person familiar with the matter said Monday.

Six tankers have been attacked outside the Gulf since early May, with the U.S. blaming Iran for the incidents, a charge Tehran denies. Insurance costs for covering tankers and their cargoes jumped as much as tenfold in the wake of the incidents. Some owners were initially wary of sending vessels to the region, although that reticence appears to have subsided.

The prospects of a showdown between the U.S. and Iran have spiked since the Trump administration quit the multiparty nuclear accord with Iran a year ago and re-imposed sanctions. In early May, the U.S. tightened penalties on buyers of Iranian oil prompting Iran to begin scaling back its commitments under the deal.

Iran said this week it’s enriching uranium beyond the agreed cap and would gradually roll back compliance unless European signatories find ways to ensure it can sell its oil and access the global financial system.