Trump has recently veered between saying that Washington needs no help to secure the vital waterway for oil tankers, and then lashing out at other countries for failing to help.

"Without the U.S.A., NATO IS A PAPER TIGER!" Trump posted on his Truth Social network.

"They didn't want to join the fight to stop a Nuclear Powered Iran. Now that fight is Militarily WON, with very little danger for them, they complain about the high oil prices they are forced to pay, but don't want to help open the Strait of Hormuz, a simple military maneuver that is the single reason for the high oil prices.

"So easy for them to do, with so little risk. COWARDS, and we will REMEMBER!"

The 79-year-old Republican, a long-term skeptic of the Western military alliance, has launched a series of diatribes against NATO in recent days.

On Thursday, six major international powers, including Britain, France, Germany and Japan said they were ready to "contribute to appropriate efforts" to secure the Strait of Hormuz.

But they have not formally committed to any mission to work in the crucial waterway -- while other allies such as Germany and Italy have ruled out doing anything before a truce in the Middle East war.

None of the countries Trump has called on to help was consulted before the US-Israeli mission started.

An effective Iranian blockade has paralyzed commercial shipping through the crucial maritime chokepoint, which in peacetime sees a fifth of global crude oil and liquefied natural gas pass through it.

Global oil prices have spiked as a result of the war, which erupted on February 28 when the United States and Israel began bombing Iran, leading Tehran to retaliate with strikes across the Gulf region.