Trump says NATO's refusal to help on Iran is 'very foolish'

President Donald Trump on Tuesday said the United States had been informed by most of its NATO allies that they did not want to get involved with the country's military operation in Iran, a move he described as a "very foolish mistake".

But Trump gave no indication that he plans to punish NATO allies for their stances, as he took questions from reporters in the Oval Office during the St. Patrick's Day visit of Irish Prime Minister Micheal Martin.

Trump said NATO countries were supportive of the joint US-Israeli war, which has now entered its third week, even as they did not want to get involved.

"I think NATO is making a very foolish mistake," Trump said. "Everyone agrees with us, but they don't want to help. And we, you know, we as the United States have to remember that because we think it's pretty shocking," he added.

As for whether he would retaliate against NATO allies for holding back, Trump said he had "nothing currently in mind."

The president in the past has threatened to withdraw the United States from NATO but did not bring that up on Tuesday.

Trump called on nations to help police the Strait of Hormuz, through which 20 per cent of the world's oil is transported, after Iran responded to US-Israeli attacks by using drones, missiles and mines to effectively close the channel for tankers.

But several US allies said on Monday they had no immediate plans to send ships to help unblock the strait, effectively rebuffing Trump's plea for military support.

Earlier on Tuesday, Trump wrote on Truth Social that "Because of the fact that we have had such Military Success, we no longer 'need,' or desire, the NATO Countries’ assistance - WE NEVER DID!" He singled out Japan, Australia and South Korea.