Donald Trump prompted stark warnings on Sunday that his remarks against NATO threatened the military alliance, after a campaign speech renewed doubts over the US commitment to the mutual defense treaty if the former president wins in November.
Speaking at a campaign rally in South Carolina on Saturday, Trump described what he said was a conversation with a fellow head of state at an unspecified NATO meeting.
"One of the presidents of a big country stood up and said, 'Well, sir, if we don't pay, and we're attacked by Russia, will you protect us?' I said, 'You didn't pay, you're delinquent?'"
"No, I would not protect you. In fact, I would encourage them to do whatever the hell they want."
Trump has regularly criticized allies of the North Atlantic Treaty Organization for not meeting a goal of spending at least two percent of GDP on defense.
"You got to pay. You got to pay your bills," Trump, who is almost certain to be the Republican nominee for the November presidential election, said Saturday.
Trump's remark comes after Senate Republicans on Wednesday rejected a bipartisan bill that would have included sorely needed funding for Ukraine, plus aid for ally Israel, along with reforms to address the US-Mexico border crisis, AFP reported.
The US Senate is now considering a foreign aid package that decouples the aid from the border issue entirely. It could see a key procedural vote on Sunday.
The $95 billion package includes funding for Israel and Taiwan, but the majority would go toward helping Ukraine rearm as it enters a third year of war since Russian President Vladimir Putin ordered a full-scale invasion.
The White House hit back at Trump's assertions, touting President Joe Biden's efforts to bolster alliances around the globe.
"Encouraging invasions of our closest allies by murderous regimes is appalling and unhinged," White House spokesman Andrew Bates said in a statement Saturday night.
NATO chief Jens Stoltenberg warned Sunday that "any suggestion that allies will not defend each other undermines all of our security, including that of the US."
European Council President Charles Michel also denounced the comments as "reckless," saying they can "serve only Putin's interest."
Republican Senator Marco Rubio, who has endorsed Trump for his party's nomination, defended the ex-president on Sunday as "telling a story" about something that happened in the past.
"He doesn't talk like a traditional politician," the Florida senator told CNN's "State of the Union."
"By the way, Donald Trump was president and he didn't pull us out of NATO. In fact, American troops were stationed throughout NATO" during his term, Rubio said.
Stoltenberg, for his part, said he expects that "regardless of who wins the presidential election the US will remain a strong and committed NATO ally."
At the South Carolina rally, Trump also needled Nikki Haley, his former UN ambassador, who is challenging him for the Republican nomination but badly trailing in the race.
Haley, when asked Sunday about Trump's NATO remarks, alleged her former boss was taking Putin's side.
"What bothers me about this is, don't take the side of a thug who kills his opponents. Don't take the side of someone who has gone in and invaded a country and half a million people have died or been wounded," Haley told CBS News' "Face the Nation."
She also defended her husband Michael Haley, who is on a military deployment in Africa, after Trump mocked his absence from the campaign trail.
"This isn't personal about me and Michael. This is what it says to every member who sacrifices for us," said the former South Carolina governor.
"We can't have someone that sits and mocks our men and women trying to protect America. It's a pattern of chaos," she said.