CNN  — 

Former President Donald Trump on Saturday said he would encourage Russia to do “whatever the hell they want” to any NATO member country that doesn’t meet spending guidelines on defense in a stunning admission he would not abide by the collective-defense clause at the heart of the alliance if reelected.

“NATO was busted until I came along,” Trump said at a rally in Conway, South Carolina. “I said, ‘Everybody’s gonna pay.’ They said, ‘Well, if we don’t pay, are you still going to protect us?’ I said, ‘Absolutely not.’ They couldn’t believe the answer.”

Trump said “one of the presidents of a big country” at one point asked him whether the US would still defend the country if they were invaded by Russia even if they “don’t pay.”

“No, I would not protect you,” Trump recalled telling that president. “In fact, I would encourage them to do whatever the hell they want. You got to pay. You got to pay your bills.”

President Joe Biden said Sunday that Trump “is making it clear that he will abandon our NATO allies” and outlined the potential consequences of Trump’s comments.

“Trump’s admission that he intends to give Putin a greenlight for more war and violence, to continue his brutal assault against a free Ukraine, and to expand his aggression to the people of Poland and the Baltic States are appalling and dangerous,” Biden said in a statement via his campaign.

NATO Secretary General Jens Stoltenberg, meanwhile, said Sunday that Trump’s comments about the alliance put European and American soldiers at risk.

“Any attack on NATO will be met with a united and forceful response,” Stoltenberg said in a statement. “Any suggestion that allies will not defend each other undermines all of our security, including that of the US, and puts American and European soldiers at increased risk.”

European Council President Charles Michel on Sunday described comments from Trump on NATO “reckless,” adding they “serve only Putin’s interest.”

At the core of the North Atlantic Treaty Organization and enshrined in Article 5 of the treaty is the promise of collective defense — that an attack on one member nation is an attack on all the nations in the alliance. Trump has long complained about the amount other countries in NATO spend on defense compared with the United States and has repeatedly threatened to withdraw the US from NATO. But his comments Saturday are his most direct indication he does not intend to defend NATO allies from Russian attack if he is reelected.

Trump has for years inaccurately described how NATO funding works. NATO has a target that each member country spends a minimum of 2% of gross domestic product on defense, and most countries are not meeting that target. But the figure is a guideline and not a binding contract, nor does it create “bills”; member countries haven’t been failing to pay their share of NATO’s common budget to run the organization.

Republican Sen. Marco Rubio, who has endorsed Trump, said Sunday he had “zero concerns” about the former president’s NATO comments.

Rubio told CNN’s Jake Tapper on “State of the Union” that Trump was merely reflecting on an anecdote from his presidency, arguing member nations weren’t “paying their dues” until Trump “used leverage” to push NATO countries to “step up to the plate.”

“Trump’s just the first one to express it in these terms,” the Florida Republican said.

As president, Trump privately threatened multiple times to withdraw the United States from NATO, according to The New York Times. Trump has described NATO as “obsolete” and has aligned himself with Russian President Vladimir Putin, who wants to weaken the alliance. Trump has long praised Putin and went as far as to side with the Russian leader over the US intelligence community over Russia’s interference in the 2016 presidential election.

This story has been updated with additional developments.

CNN’s Kaanita Iyer, Daniel Dale, Marshall Cohen, Veronica Stracqualursi, Jim Acosta, Kevin Liptak, Aileen Graef, Michelle Shen and Martin Goillandeau contributed to this report.