LONDON — Britain's Foreign Secretary Jeremy Hunt warned Iran of "serious consequences" if it does not release a British-flagged oil tanker it seized in the strategic Strait of Hormuz waterway on Friday, although he ruled out "military options."

Hunt announced later in a tweet that he had spoken with Iranian foreign minister Mohammad Javad Zarif and "expressed extreme disappointment" that Iran had "behaved in the opposite way" of trying to deescalate the situation.

The seizing of the "Stena Impero" potentially marks the most significant escalation in tensions between Iran and the West since they began rising in May, about a year after the United States pulled out of an international accord aimed at Iran's nuclear program.

The Pentagon announced it authorized the movement of troops to Saudi Arabia as an "additional deterrent," adding to the 1,000 troops deployed to the Middle East in June.

The showdown has caused concerns around the globe, with each maneuver bringing fear that any misunderstanding or misstep by either side could lead to war.

"It is essential that freedom of navigation is maintained and that all ships can move safely and freely in the region," Hunt said late Friday, ahead of an emergency government meeting. He subsequently told British media that "we’re looking at a diplomatic way to resolve the situation, but we are very clear that it must be resolved."

About a fifth of the world's crude oil exports passes through the Strait of Hormuz.

Iran’s Revolutionary Guard Corps (IRGC) said Friday that the "Stena Impero" was taken to an Iranian port because it was not complying with "international maritime laws and regulations." On Saturday, Iran's state-run IRNA news agency reported that the "Stena Impero" collided with an Iranian fishing boat, causing it damage, and then failed to respond to calls from the smaller craft. The fishing boat informed Iran’s Ports and Maritime Organization, which notified the IRGC. The IRGC launched an investigation.

FARS, Iran's semi-official news agency, later released video showing the IRGC seizing the ship.

Iran's Revolutionary Guard also released a new, high-quality video of the incident, showing commandos in black ski masks rappelling from a helicopter onto the vessel.

A statement from Stena Bulk, which owns the seized tanker, said the ship had 23 crew members aboard when it was seized. They are from India, Russia, Latvia and the Philippines. There were no reports suggesting of any of them were injured.

Another British ship was briefly detained Friday before allowed to go. The owner of the Liberian-flagged, but British-owned, tanker said it was boarded by armed guards. The "Mesdar" vessel has left Iran’s territorial waters, Iran state media said.

"This only goes to show what I’m saying about Iran: trouble," President Donald Trump told reporters at the White House. "Nothing but trouble."

Trump declined to say whether the moves by Iran crossed a "red line" or how the U.S. might respond. He noted the U.S. has a maritime security agreement with Britain.

The latest incident follows a threat by Iran to seize a British oil tanker in the Persian Gulf after British Royal Marines earlier this month helped capture an Iranian tanker off Gibraltar, in the Mediterranean Sea, suspected of carrying oil to Syria in breach of European Union sanctions. Iran denied the ship was on its way to Syria.

Suggesting the tanker seizure could have been a retaliatory act, FARS reported a spokesperson for Iran's Guardian Council, Abbas Ali Kadkhodayee, as saying, "The rule of reciprocal action is well-known in international law which is used against the foul measures of a government," adding that the seizure of the ship was a "correct measure...based on international rights."

U.S. patrol aircraft are in the vicinity monitoring the situation in the Strait of Hormuz, and Naval Forces Central Command has been in contact with American ships in the area to ensure their safety, a Department of Defense official said. Britain has sent additional warships to the area and been escorting oil tankers in the region.

U.S. Central Command said it in the process of developing a "multinational maritime effort," called "Operation Sentinel," to increase security of key Middle East waterways.

Last month, Trump abruptly canceled a planned retaliatory attack on Iran after the country downed an unmanned U.S. drone, but his administration has kept up a policy of trying to squeeze Iran's leaders with stiff economic sanctions. Days after he pulled back the strikes on Iran, Trump threatened to use "overwhelming force" against Iran if it attacked any U.S. assets or personnel. Trump announced that the U.S. "destroyed" an Iranian drone on Thursday. Iran said there is no evidence for that.

"If (Stena Impero) has been taken to Bandar Abbas then that’s an important Iranian military port and I think any military options will therefore be extremely unwise," Tom Tugendhat, chairman of Britain's parliamentary Foreign Affairs Committee, told the BBC.

Contributing: Doug Stanglin, Nicholas Wu, David Jackson, Donovan Slack and John Fritze, from Washington, D.C.; Associated Press