US President Donald Trump has ramped up calls for other nations to help American forces in the war on Iran, warning of a “very bad” future for NATO if they don’t.

“It’s only appropriate that people who are the beneficiaries of the Strait [of Hormuz] will help to make sure that nothing bad happens there,” Trump told Britain’s Financial Times in a phone interview on Sunday (US time).

“If there’s no response or if it’s a negative response, I think it will be very bad for the future of NATO.”

Asked what assistance he sought, Trump said “whatever it takes”, including minesweepers.

In a social media post on Saturday, Trump urged China, France, Japan, South Korea, Britain and other nations to send warships to secure the Strait of Hormuz, which handles about 20 per cent of the world’s oil supplies.

“The Countries of the World that receive ​Oil through the Hormuz Strait must take care of that passage, and we will help — A LOT!” he wrote.

“The US will also coordinate with those Countries so that everything goes quickly, smoothly, and well.”

None of those countries has yet given any immediate indication they will.

Later, aboard Air Force One, Trump said his administration was talking to seven countries about helping secure the Strait of Hormuz.

“I’m demanding that these countries come in and protect their own territory, because it is their territory,” he said.

Though ‌he declined to ‌identify the governments that ⁠his administration had contacted, Trump said last weekend he expected many countries would send warships to allow ​shipping through the vital waterway.

On Monday, Australia ruled out sending ships to assist in US-led efforts to protect oil tankers from Iranian attacks in the area.

“We’ve been very clear about what our contribution is in relation to our requests, and so far that is to the UAE, obviously providing aircraft to assist with defence, particularly given the number of Australians that are in that area in particular,” Transport Minister Catherine King told Radio National on Monday.

“But we won’t be sending a ship to the Strait of Hormuz. We know how incredibly important that is. That’s not something that we’ve been asked or we’re contributing.”

In his interview with the Financial Times, Trump also boosted American assistance to Ukraine in its war against Russia.

“We didn’t have to help them with Ukraine. … Now we’ll see if they help us. Because I’ve long said that we’ll be there for them but they won’t be there for us,” he said.

He also repeated his frustration with British Prime Minister Keir Starmer, over his lack of immediate support for the US-Israeli strikes on Iran.

“The UK might be considered the No. 1 ally, the longest serving, etc., and when I asked for them to come, they didn’t want to come,” Trump said.

“As soon as we basically wiped out the danger capacity from Iran, they said, ‘Oh, well we’ll send two ships’, and I said, ‘We need these ships before we win, not after we win’. I’ve long said that NATO is a one-way street.”

Trump and Starmer also spoke by phone on Sunday about the issues in the Strait of Hormuz.

“The leaders discussed the ongoing situation in the Middle East and the importance of reopening the Strait of Hormuz to end the disruption to global shipping, which is driving up costs worldwide,” Starmer’s office said.

“The Prime Minister also expressed his condolences for the American service personnel who have lost their lives during the conflict.”

NATO is a European and North American defence alliance that is intended to promote peace and stability and to safeguard the security of its members. It is not meant to aid a member state that starts a war.

Trump said he was also considering putting off his planned summit with Chinese leader Xi Jinping as he urges Beijing to help address disruptions in the waterway.

“I think China should help too because China gets 90 per cent of its oil from the straits,” Trump said.

He said he would prefer to know Beijing’s position before he and Xi are due to meet later in March.

“We’d like to know before that. It’s [two weeks is] a long time,” he said.