"I love the king, King Salman, but I said, 'King, we're protecting you,'" Trump says at a campaign rally in Mississippi, without elaborating on when he spoke to King Salman bin Abdulaziz.
US President Donald Trump on Tuesday said Saudi Arabia's king "might not be there for two weeks" without US military support, as he sought to pressure the close American ally over rising oil prices.
Speaking at a campaign rally in Mississippi, Trump said, "I love the king, King Salman, but I said, 'King, we're protecting you. You might not be there for two weeks without us. You have to pay for your military, you have to pay.'"
Trump didn't elaborate on when he spoke to the king. Trump and King Salman last shared a reported telephone call on Saturday.
Despite the harsh words, the Trump administration has had a close relationship with Saudi Arabia, which it views as a bulwark against Iran's ambitions in the region.
Trump made Saudi Arabia his first stop on his maiden international trip as president last year.
Trump called King Salman on Saturday and they discussed efforts being made to maintain supplies to ensure oil market stability and global economic growth, according to Saudi state news agency SPA.
Saudi Arabia is the world's top oil exporter and the de facto leader of OPEC, which has been criticised by Trump for high oil prices.
Benchmark Brent crude oil is near $85 a barrel – a four-year high – and analysts say it could reach $100.
US gasoline prices are up ahead of November midterm elections.
OPEC 'ripping off the rest of the world'
Speaking at the United Nations General Assembly in New York last month, Trump said OPEC members were "as usual ripping off the rest of the world."
"We defend many of these nations for nothing, and then they take advantage of us by giving us high oil prices. Not good. We want them to stop raising prices, we want them to start lowering prices," Trump said.
He has also pressed other US allies, such as Japan, South Korea and Germany, to take more of the financial burden of their defence.