Washington (CNN) — President Joe Biden on Tuesday slammed Donald Trump after the former president said he would encourage Russia to invade countries that don’t meet their NATO obligations, saying such comments amount to bowing down to Vladimir Putin.

The remarks – Biden’s latest criticism of Trump from the White House – are some of his harshest criticism of his likely rival on foreign policy to date.

Speaking Saturday at a rally in South Carolina, Trump 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. Biden said those comments sent a “dangerous and shocking” signal.

“Can you imagine a former president of the United States saying that?” Biden asked incredulously from the State Dining Room. “The whole world heard it. The worst thing is he means it.”

Biden began his speech by encouraging the House of Representatives to “immediately” hold a vote on the Senate-passed, $95 billion supplemental aid package that would provide assistance to Ukraine, Israel and US partners in the Indo-Pacific region, as well as humanitarian assistance to Palestinians in the Gaza Strip.

More than $60 billion from the Senate package would have been allocated to Ukraine, as the country prepares to mark the second anniversary of its full-scale invasion by Russia. Previous attempts to pass an aid package – combined with a border security bill – were scuttled after Trump came out in opposition.

Trump’s comment drew immediate consternation, not only from the American foreign policy establishment but from NATO allies, who have watched warily as Russia proceeds with its invasion of Ukraine.

For Biden, who has spent much of his career working on issues related to transatlantic security, the remark was particularly galling. When he heard about the remarks afterward, the president was aghast, according to a person familiar with the matter. He later issued a statement through his campaign decrying the sentiment.

The White House criticized Trump’s comments shortly after they were made.

“Encouraging invasions of our closest allies by murderous regimes is appalling and unhinged – and it endangers American national security, global stability, and our economy at home,” White House spokesperson Andrew Bates said in a statement on Saturday.

But Biden’s criticism of Trump from the White House went a step further. In a speech that mentioned Trump by name at least a half-dozen times, Biden sought to forcefully rebut questions about American commitment to its allies.

“No other president in our history has bowed down to a Russian dictator,” Biden went on. “Let me say this as clearly as I can: I never will. For God’s sake, it’s dumb. It’s shameful. It’s dangerous. It’s un-American.”

On Tuesday, Biden spent a significant portion of his speech on Ukraine aid going after Trump for the remark, which he said undercut longstanding US values.

“When America gives its word, it means something. When we make a commitment, we keep it and NATO is a sacred commitment,” Biden said.

“Donald Trump looks at this as if it’s a burden,” he added.

He said Trump viewed the defense alliance as a “protection racket” and didn’t understand its role in protecting freedom and security.

“For Trump, principles never matter. Everything is transactional,” Biden said.

He said American adversaries “all cheered” when they heard Trump’s comments. “I will not walk away. I can’t imagine any other president walking away,” Biden said.

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