The US president has previously threatened to withdraw his country from the military alliance and repeatedly criticised its members for failing to support Washington’s war on Iran.

“Nato wasn’t there for us, and they won’t be there for us in the future!” he wrote on his Truth Social platform on Wednesday morning.

Europe is accelerating a fallback plan to ensure the continent can defend itself if Washington abandons Nato amid the standoff.

Plans involve reinforcing US military assets with the alliance’s own and adding more Europeans into command-and-control roles, according to officials cited by The Wall Street Journal.

He made the comment as the US Central Command said a US blockade of Iranian ports had been “fully implemented”, with American forces maintaining maritime superiority in the Middle East.

In a statement, Adml Brad Cooper, the Centcom commander, said: “In less than 36 hours since the blockade was implemented, US forces have completely halted economic trade going into and out of Iran by sea.”