The US president says the US "may not" help alliance members if asked to do so.
"We spend hundreds of billions of dollars every year on NATO - hundreds - to protect them, and we would have always stood up for them, but now, given their actions, we don't have to do that anymore," Donald Trump said at an event in Miami on Friday.
Trump has previously expressed frustration that he perceives NATO countries as unwilling to help open the Strait of Hormuz.
Dutch Prime Minister Mark Rutte said on Sunday that it was all about the countries not having had the same time to assess the situation. He also highlighted that 22 countries, including several NATO members, had said they were willing to help make shipping in the strait safe.
"The US has been planning this operation for months but has not been able to share it with its allies for security reasons, which I understand," Rutte told Fox News.
As a result of the war in the Middle East, Iran has essentially closed the Strait of Hormuz, which is important for oil trade.
