British Warship Forces Three Iranian Boats to Back off After they Sought to Block a British Tanker

LONDON — A British warship forced three Iranian boats to back off after they sought to block a British tanker from passing through the Strait of Hormuz, the Defense Ministry said on Thursday, in the latest escalation of tensions between Tehran and the West.

“Contrary to international law, three Iranian vessels attempted to impede the passage of a commercial vessel, British Heritage, through the Strait of Hormuz,” the British government said. “We are concerned by this action and continue to urge the Iranian authorities to de-escalate the situation in the region.”

The most recent escalation began in May, after the Trump administration implemented comprehensive sanctions intended to cut off all Iranian oil exports as part of an effort to pressure Tehran into accepting sweeping new restrictions on its military activities and its nuclear program.

The United States was on the verge of launching a missile strike against Iran last month in retaliation for the shooting down of an American surveillance drone, but President Trump said he called off the military action at the last minute.

Tensions between Tehran and London rose last week, when the British played a crucial role in the seizure of an Iranian tanker off the coast of Gibraltar as it was carrying oil bound for Syria, on suspicion that it was violating European Union sanctions. Iranian officials called the British seizure “an act of piracy.”

In its statement on Thursday, the British government said three Iranian boats had attempted to stop the British Heritage in the early morning as it headed toward the Strait of Hormuz, a narrow passage out of the Persian Gulf that is a vital channel for international oil supplies.

A British warship, the Montrose, had been escorting the tanker in an effort to guard against any Iranian interference. After a short standoff, the British warned the three Iranian boats to back away and they did, the British government said in its statement.

“H.M.S. Montrose 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 Defense Ministry said in a statement.

Iran denied any attempt to stop the tanker, according to Iranian news agencies.