(This December 31, 2018 story corrects unit in paragraph 5 to remove words “per hour”.)

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LONDON (Reuters) - Iran’s Revolutionary Guards said on Monday they plan to upgrade their speed boats in the Gulf with radar-evading stealth technology and new missile launchers as tensions rise between Tehran and Washington in the vital oil shipping route.

Ending a long absence of U.S. aircraft carriers in the region, the USS John C. Stennis entered the Gulf last week, and was shadowed by the Revolutionary Guards’ speed boats.

There have been periodic confrontations between the Revolutionary Guards vessels and U.S. military in the Gulf, although the number of incidents has dropped in recent months.

“We are trying to increase the agility of the Guards’ speed boats and equip them with stealth technology to facilitate their operations,” Alireza Tangsiri, the Revolutionary Guards’ navy chief, was quoted as saying by the state news agency IRNA.

Tangsiri also said the speed boats will be equipped with new missiles, and their speed will reach 80 knots.

He did not elaborate on whether Iran had already mastered these technologies or if they were still in the study phase.

Iran says it has been developing its own stealth technology for fighter jets and vessels, but the prototypes it has unveiled in recent years have mostly been met with derision by defense experts.

The Revolutionary Guards last week launched war games in the Gulf, where third of the world’s sea-borne oil passes through, and warned that its forces were ready to respond to any hostile U.S. action.

In an indirect threat to Saudi Arabia and other U.S. allies in the region, the head of the Iranian armed forces warned that any Iranian confrontation with U.S. forces might also target Gulf nations that he said had invited them into the region.

“Iran’s regional enemies should know that alongside a pacifist doctrine, Iran has a powerful military force that are ready to protect Iran’s territorial integrity, and also hold accountable countries that proposed (the U.S. presence),” Major General Mohammad Bagheri was quoted as saying by Fars news agency.

A U.S.-Iranian war of words has escalated since U.S. President Donald Trump took Washington out of a world powers’ nuclear deal with Iran in May, and reimposed sanctions on its banking and energy sectors.

Iran has warned that if it cannot sell its oil due to U.S. pressure, then no other regional country will be allowed to do so either, threatening to block the Strait of Hormuz in the Gulf.

The Guards’ naval arm lacks a strong conventional fleet. However, it has many speed boats and portable anti-ship missile launchers, and can lay mines.