One way that Iran could potentially retaliate for the American strikes on three of its nuclear sites, analysts say, would be to shut down the Strait of Hormuz, a key shipping route for oil and gas.

In meetings at the White House, senior military officials have raised the need to prepare for that possibility, after Iranian officials threatened to mine the strait, a narrow 150km waterway connecting the Persian Gulf to the open ocean. Such a move could pin any US Navy ships in the Persian Gulf.

Three empty oil and chemical tankers have diverted away from the Strait of Hormuz, Marine Traffic ship tracking data showed on Monday. The Marie C and Red
Ruby, which were in ballast rather than carrying cargo and previously sailing towards the Strait, dropped anchor near Fujairah off the UAE coast.

The Kohzan Maru was sailing in the Gulf of Oman close to Omani waters, according to data on the MarineTraffic platform.

Japan’s Nippon Yusen and Mitsui O.S.K. Lines said on Monday they had instructed their vessels to minimise the time spent in the Gulf as they continue to transit the Strait of Hormuz.

Iran’s parliament on Sunday approved a measure to close the strait, Iran’s Press TV reported, but any such move would require approval from the Supreme National Security Council.

Iran has threatened to close the strait in the past but has never done so.

In more than a week of fighting between Israel and Iran, Israel’s military has steered clear of hitting Iranian naval assets. So while Iran’s ability to respond to attacks has been severely damaged, it has a robust navy and maintains operatives across the region, where the US has more than 40,000 troops. Iran also has an array of mines that its navy could lay in the Strait of Hormuz, which hugs a portion of Iran’s southern border.

A quarter of the world’s oil and 20 per cent of the world’s liquefied natural gas passes through the Strait of Hormuz, so mining the choke point would cause oil and gas prices to soar. The majority of those fuels go to Asia, meaning that countries there would most likely be severely affected by any closure. The US and other countries would feel the effects in the form of higher energy costs. That has spurred forecasts of oil surging to $100 a barrel.

Closing the waterway could isolate American minesweepers in the Persian Gulf on one side of the strait. Two defence officials indicated that the navy was looking to disperse its ships in the gulf so that they would be less vulnerable. A navy official declined to comment, citing operational security. The officials spoke on condition of anonymity because they were not authorised to speak publicly.

“Many of Iran’s options are the strategic equivalent of a suicide bombing,” said Karim Sadjadpour, an Iran policy expert at the Carnegie Endowment for International Peace. “They can do enormous damage to others if they mine the Strait of Hormuz, destroy regional oil facilities and rain a missile barrage against Israel, but they may not survive the blowback.”

But Iran can make it hugely expensive, and dangerous, for the US Navy to have to conduct what would most likely be a weekslong mine-clearing operation in the Strait of Hormuz, according to one former naval officer who was stationed on a minesweeper in the Persian Gulf. He and other Navy officers said that clearing the strait could also put American sailors directly in harm’s way.

Mining the strait would also inflict severe economic damage in Iran.