Biden campaign attacks Trump's comments threatening NATO in new ad

President Joe Biden and Vice President Kamala Harris are continuing to attack former President Donald Trump for saying he would "encourage" Russia to "do whatever the hell they want" to NATO member countries that are "delinquent" in defense spending.

The Biden-Harris campaign released a new ad title "Walk Away" on Friday highlighting Trump's comments they call "traitorous," hours after the reported death of Alexei Navalny, the longtime Russian opposition politician and critic of Russian President Vladimir Putin.

"Trump wants to walk away from NATO. He's even given Putin and Russia the green light to attack America's allies," the ad's narrator says, before quoting Trump at his rally last Saturday in South Carolina, saying, "I would encourage them to do whatever the hell they want."

"No president has ever said anything like it," the narrator ads. "It's shameful. It's weak. It's dangerous. It's un-American."

The three-week, six-figure ad campaign will run through Super Tuesday and target voters in the battleground states of Michigan, Wisconsin and Pennsylvania, the campaign said, places that are "home to more than 2.5 million Americans who identify as Polish, Finnish, Norwegian, Lithuanian, Latvian, or Estonian -- all NATO countries that border Russia and face the threat of an expansion of Putin's aggression in Ukraine."

Biden used similar language in blaming Navalny's death squarely on Putin in remarks at the White House on Friday, arguing Americans should "reject" what he called the "dangerous statements" from Trump.

"This is an outrageous thing for a president to say. I can't fathom -- can't fathom, from Truman on, they're rolling over in their graves hearing this," he said.

"Now is the time for even great unity among our NATO allies to stand up to the threat that Putin's Russia poses," he added.

Harris, speaking at the Munich Security Conference on Friday, also defended the Biden administration's approach to foreign policy and warned against those who, instead, "embrace dictators," in a thinly veiled attack against Trump.

"They suggest it is in the best interest of the American people to isolate ourselves from the world, to flout common understandings among nations, to embrace dictators and adopt the repressive tactics and abandon commitments to our allies in favor of unilateral action," Harris said.

"Let me be clear, that world view is dangerous, destabilizing and indeed shortsighted. That view would weaken American and undermine global stability and undermine global prosperity. President Biden and I therefore reject that view," she added.

The rebuke from Harris comes after Biden on Tuesday blasted Trump's comments from the White House, calling them "shocking" and "un-American" -- and after Trump doubled down on his message to NATO in a social media post on Monday, saying, "YOU MUST PAY."

Trump again stood by the comments at a rally on Wednesday in North Charleston, South Carolina.

"Look, if they're not going to pay, we're not going to protect. OK?" he said.

Biden-Harris campaign manager Julie Chavez Rodriguez echoed Biden's condemnation of the threats to the NATO alliance in announcing the campaign's new ad on Friday.

"President Biden is right: Trump's attempts to appease dictators like Putin are 'dumb,' 'shameful,' 'dangerous,' and 'un-American,'" she said in a statement. "The bottom line is that the only person Donald Trump is loyal to is Donald Trump – not to our allies and certainly not to the American people. And while he thinks that sucking up to Putin and other dictators will make him strong, the American people know him for who he truly is: a coward and a loser."

ABC News' Justin Gomez and Sarah Beth Hensley contributed to this report.