Donald Trump said he had warned Nato allies that he would encourage Russia to do “whatever the hell they want” if alliance members failed to meet defence spending targets, highlighting the risk to the military pact if he wins a new term in the White House.

Trump’s comments came during a campaign rally ahead of the Republican presidential primary in South Carolina this month, which could help him to seal his party’s nomination to contest the November election against Joe Biden.

The former US president, who has long been a critic of Nato and who had warm relations with Russian president Vladimir Putin, told his supporters that “Nato was busted until I came along”. He said that during his term in office he had insisted to European allies that “everybody’s going to pay”.