Iran’s supreme leader Ayatollah Ali Khamenei gestures to the commanders of Revolutionary Guards during a meeting in Tehran.

A senior official in Iran’s elite Revolutionary Guards on Wednesday accused the United States of provoking tensions after two separate incidents in the Gulf last week.

“A US Navy ship crossing the Strait of Hormuz changed its international route and approached to within 550 metres of Revolutionary Guards’ boats in an unprofessional way,” Mehdi Hashemi told the Guard’s website Sepahnews.

He said actions by the United States and the United Kingdom in recent days showed they have “harmful, illegitimate and provocative objectives”.

“Not only do they not want stability and security in the Persian Gulf and the Strait of Hormuz, but they seek to create tensions and a crisis,” he said.

The Pentagon on Monday blasted the “unprofessional” behaviour of the Iranian navy.

It said an Iranian frigate last Thursday came within 150 yards (metres) of the civilian-crewed USNS Invincible.

Then on Saturday, a number of small assault craft came within 350 yards of the Invincible and other ships.

In both cases, the US ship had to change course to avoid a collision, Pentagon spokesman Navy Captain Jeff Davis said.

Davis accused Iranian forces of “a combination of unsafe or unprofessional behavior” and warned that such incidents could cause a miscalculation or an accidental provocation.

He said Iranian actions in the crowded waters of the Gulf had been improving of late.

The Pentagon has previously voiced concern over a string of high-profile incidents in waters off Iran. It has accused the Iranian Revolutionary Guard Corps (IRGC) of conducting risky maneuvers around US vessels, including somewhere the Americans have had to fire warning shots.

The USNS Invincible is equipped with powerful radar equipment to track ballistic missile trajectories.

The prefix “USNS” means the ship belongs to the US Navy but is unarmed or only lightly armed.