Trump: NATO faces 'very bad' future if it doesn't help with Iran

US president Donald Trump has suggested that NATO may be have a "very bad" future if allies don't help ensure safe passage for commercial shipping through the Strait of Hormuz, which is vital for global oil transport, the Financial Times (FT) reported late on Sunday.

"It's only appropriate that people who are the beneficiaries of the Strait will help to make sure that nothing bad happens there," the FT quoted Trump as saying in a eight-minute phone conversation.

"If there's no response or if it's a negative response I think it will be very bad for the future of NATO," Trump told the FT, stressing that, unlike the United States, Europe and China are heavily reliant on oil from the Gulf.

Just a day earlier, Trump had called on "many countries" to provide military support to help ensure safe passage for commercial shipping through the strait.

Traffic through the narrow waterway has nearly collapsed amid security concerns following US-Israeli attacks on Iran and Tehran's response. Around one-fifth of global oil shipments normally pass through the strait every day.

"We're hitting them very hard," Trump told the FT of Iran. "They've got nothing left but to make a little trouble in the Strait but these people are beneficiaries and they ought to help us police it. We'll help them. But they should also be there. You sort of need a lot of people to watch over a few."

Trump also hinted that the US "may delay" an expected trip to China for a summit with Chinese leader Xi Jinping, which media reports had indicated could begin at the end of March.

"I think China should help too because China gets 90 per cent of its oil from the Straits [sic]," Trump said. "We'd like to know before that. It's [two weeks is] a long time," the FT quoted him as saying.