“The United States reserves the right to defend our personnel, our facilities and interests, and calls upon all nations to condemn Iran’s attempts to disrupt freedom of navigation and global commerce,” he said. “I also call on other nations to protect their ships as they go through the strait and to work with us in the future.”

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Trump’s disclosure of the drone incident came hours after Iran’s Islamic Revolutionary Guard Corps said it was responsible for seizing a tanker that went missing over the weekend in the strait, which controls access to the Persian Gulf and the oil that flows through it.

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The tanker, based in the United Arab Emirates, and its 12-member crew were detained after they were found to be smuggling Iranian fuel, according to a statement by the Revolutionary Guard. The statement appeared to contradict an earlier claim by Iran’s Foreign Ministry that Iranian authorities had rescued the ship after it broke down.

Iranian officials did not immediately comment on the downed drone. The Fars News Agency, which is close to the Revolutionary Guard, noted Trump’s statement but offered no further remarks.

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Pentagon spokesman Jonathan Hoffman confirmed the action, which he said was taken “to ensure the safety of the ship and its crew.” U.S. defense officials declined to describe the incident further, aside from releasing a one-paragraph statement.

It was not clear whether the unmanned aircraft was armed, or how the Navy brought it down, but U.S. military officials have watched with concern as Iranian-backed Yemeni rebels have used “suicide drones” packed with explosives in other parts of the region.

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A defense official told CNN that the drone was taken down with electronic jamming after it came within a threatening distance of the ship.

The Boxer is part of an amphibious force that includes more than 2,000 Marines from the 11th Marine Expeditionary Unit, which arrived in the region this week as the Pentagon seeks to prevent commercial ships from being seized or harassed by Iranian forces.

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The downing of the drone follows a string of recent incidents, including attacks on tankers, that U.S. officials say are part of an Iranian effort to harm the United States and its allies in the region. The United States has continued to exert a “maximum pressure” campaign against Iran to force it back to the negotiating table after the United States walked away from the 2015 Iran nuclear deal last year.

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Iran has responded with defiance to the effort, and tensions have escalated sharply in recent months.

In May, national security adviser John Bolton released an unusual statement saying that the United States was sending to the region a bomber task force and a naval strike group led by an aircraft carrier, rather than having the Defense Department handle the announcement.

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Last month, Trump told the Pentagon to draw up plans for a military strike on Iran after an American surveillance drone was shot down over the Strait of Hormuz. He changed his mind about it abruptly days later after realizing that it could result in as many as 150 Iranian troops being killed, he later tweeted.

Iran said its seizure of the tanker was prompted by suspicions that it was involved in smuggling Iranian fuel, but shipping experts and diplomats noted that Iran has been engaged in a major effort to conceal the origins of Iranian oil shipments to ­circumvent sanctions, which are aimed at shutting down Iran’s oil exports.

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A video posted on the website of Iran’s English-language Press TV showed Iranian boats circling and then closing in on a small tanker clearly marked with the name Riah — the same name as the UAE-based tanker that went missing. UAE officials have denied any association with the Panama-flagged tanker, its owners or its crew, although shipping records suggest that it is owned by a UAE-based company and that it has spent the past few years operating solely out of Emirati ports.

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According to the Revolutionary Guard’s statement, the tanker took delivery of 1 million liters (264,000 gallons) of smuggled Iranian fuel from several smaller Iranian fishing boats near Iran’s Larak Island in the Strait of Hormuz, a narrow waterway through which a significant amount of the world’s traded oil is transported from the Persian Gulf. The tanker was taken “by surprise” on Sunday as it headed away from Iranian waters to deliver the fuel to foreign clients “far from Iran,” the statement said.

Suspicions that Iran had seized the tanker were first raised by the U.S. military this week. The tanker made a sharp turn toward Iranian waters on Saturday, then switched off its transponders, disappearing from the map, the U.S. military said.

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But that claim was countered by a sharp denial from Iran’s Foreign Ministry, which said Iranian authorities rescued the tankerafter it emitted a distress signal, then towed it to shore for repairs.

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Iranian Foreign Minister Mohammad Javad Zarif, speaking at a briefing for journalists at the United Nations in New York, seemed unsure whether the detained tanker was the same one that his ministry said had been rescued. But, he said, the seizure of the tanker reported Thursday should be viewed in the context of Iran’s anti-smuggling efforts.

“There is a lot of smuggling out of Iran,” he said. “A lot of it goes through the Persian Gulf; a lot of it goes through our borders with Pakistan and Afghanistan. So we do things on our borders with them, we do things in the Persian Gulf, and this is one of those.”

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The claims and counterclaims surrounding the circumstances of the ship’s detention, its activities and its ownership raised many questions that could not immediately be answered.

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Other incidents in recent weeks have contributed to the heightened tensions. Iran had threatened to retaliate after the British navy seized a supertanker near Gibraltar in the Mediterranean two weeks ago as it was carrying Iranian oil to Syria. Last week, the British navy said it had thwarted an attempt by Revolutionary Guard boats to board a British tanker in the Strait of Hormuz.

The United States has accused Iran of two attacks in the vicinity of the Persian Gulf, in which magnetic limpet mines exploded against the hulls of foreign tankers in May and June. Iran has denied the charge, although it has often threatened to retaliate against the United States and world shipping if its oil exports through the Strait of Hormuz are brought to a halt.

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