Elite frogmen have been sent to the Persian Gulf to protect British ships from Iranian attack.
The SBS commandos are experts in covertly removing mines from ships’ hulls.
They will be supported by specialist Royal Navy divers, who are trained to defuse a wide range of mines.
Tensions are soaring after the Iranian Revolutionary Guard was accused of attacking ships with mines and shooting down an American spy drone.
Fears are growing that the US could slide into war with Iran after it was reported that President Trump said his forces were “cocked and loaded” for retaliatory action, before changing his mind with just 10 minutes to go.
The Special Boat Service frogmen can also launch underwater attacks against vessels, killing or capturing foreign troops attempting to sabotage shipping.
Top defence sources said they could have Shallow Water Combat Submersibles, mini-subs used by UK and US special forces.
The Pentagon accuses Iran of blasting two tankers in the Gulf after placing mines on them.
On Wednesday Iran fired the first shot, downing a US drone with a surface-to-air missile.
There are fears Iran may close the Strait of Hormuz by mining the 20 mile wide waterway or blocking it by sinking ships.
A senior defence source said last night: “The SBS is being sent to the region as part of a deterrent. One of its roles will be to gather intelligence on Iranian mining operations.
“It will work closely with Royal Navy divers who are the specialists at disarming mines and protecting shipping.
“The SBS has a more aggressive role. Everyone is hoping that the tension will be eased and Iran will back down.”
The SBS commandos, mainly recruited from the Royal Marines, complete the same selection course as the SAS and have recently seen action in Syria.
The Defence Ministry said: “We don’t comment on special forces operations.”
