Washington CNN  — 

President Donald Trump tweeted Wednesday that he has instructed the US Navy to “shoot down and destroy any and all Iranian gunboats” that harass US ships.

“I have instructed the United States Navy to shoot down and destroy any and all Iranian gunboats if they harass our ships at sea,” Trump wrote.

Later on Wednesday senior Pentagon officials said the tweet was a lawful order though it did not mark a change in the rules of engagement.

“The President issued an important warning to the Iranians. What he was emphasizing is all of our ships retain the right of self-defense and people need to be very careful in their interactions to understand the inherent right of self-defense,” Deputy Defense Secretary David Norquist told reporters at the Pentagon.

Gen. John Hyten, Vice Chairman of the Joint Chiefs of Staff said the military will “apply that clear direction from the commander in chief into lawful orders” adding that is clear to Iran that there is a line they cannot cross that would provoke a response.

“We don’t need any more direction in order to do that. I think the President’s message was crystal clear and we don’t need any more actions,” he added.

The tweet is the latest provocative threat Trump has levied against Tehran amid scrutiny of his handling of the ongoing coronavirus pandemic, and raises fears about the possibility of a miscalculation between the two longtime foes.

Tensions sharply escalated in January when the US killed Iran’s second most powerful official, Gen. Qasem Soleimani, and earlier this month, Trump, without citing any evidence, claimed that his administration had information that “Iran or its proxies are planning a sneak attack on US troops and/or assets in Iraq.” He warned of a “heavy price” to pay if such acts were carried out.

Secretary of State Mike Pompeo also commented on the tweet in a briefing at the State Department, saying the President has been clear to the State and Defense Departments “to do everything we need to do to make sure that we protect and defend our officers, our military officers, our diplomats around the world, to continue to ensure that they are secure and safe.”

CNN has reached out to the Pentagon and White House for additional comment.

Last week, the US Navy released video that it says shows Iranian naval vessels repeatedly conducting “dangerous and harassing approaches” toward US Navy warships in the North Arabian Sea and claimed that one Iranian vessel came within 10 yards of colliding with a US ship.

The video of the incident appears to show multiple Iranian-flagged vessels, with men manning guns at the front of those ships, passing in front of a US naval vessel. The guns do not appear to be pointed at the ship, which sounded a horn multiple times as the Iranian vessels approached.

On Sunday, Iran’s Islamic Revolution Guard Corps acknowledged that an incident took place, but dismissed the US version of events as a “fake Hollywood tale,” in a statement published by the Iranian News Agency.

Roughly a half hour before Trump tweeted Wednesday, “Fox & Friends,” which Trump regularly watches, aired a segment about the incident, as well as a report on Iran launching its first military satellite into orbit. Iran’s Islamic Revolutionary Guard Corps said the launch was successful, though CNN has not been able to independently verify that.

Trump’s has not been shy to tweet about major military decisions. In 2017, he tweeted a directive to place a ban on transgender service members. The announcement blindsided military officials and led Gen. Joseph Dunford, then the chairman of the Joint Chiefs of Staff, to inform service members that there would be no immediate modifications to current policy. After a review and several legal challenges, the ban went into effect last year.

This story has been updated to include additional developments and background information.

CNN’s Barbara Starr, Ryan Browne, Jamie Crawford, Michael Conte, Sara Mazloumsaki and Ramin Mostaghim contributed to this report.