The Biden campaign is releasing a digital ad in three battleground states — Michigan, Wisconsin and Pennsylvania — with significant populations of Americans with Eastern European roots, attacking former President Donald J. Trump’s recent threat to NATO countries.

The minute-long ad highlights Mr. Trump’s claim that, while president, he had told the leaders of NATO countries that he would “encourage” Russia “to do whatever the hell they want” to nations that had not met their financial obligations to the military alliance. (Mr. Trump has long cast NATO as a kind of protection racket, twisting the facts of an unofficial commitment for member countries to increase their military spending.)

“No president has ever said anything like it,” the ad’s deep-voiced narrator says.

The spot will run through the Super Tuesday primaries on March 5 and will target voters in three states that are critical to Mr. Biden’s re-election chances. Michigan, Wisconsin and Pennsylvania 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,” the Biden campaign said in a statement.

Mr. Trump’s disparagement of NATO allies came at a time when Mr. Biden and his Democratic supporters are trying to take the focus away from voters’ concerns about the president’s age. In an address at the White House on Friday in response to the death of the Russian activist Aleksei A. Navalny, Mr. Biden condemned Mr. Trump’s comments as “outrageous” for an American president, saying that “from Truman on, they’re rolling over in their graves hearing this.” (The United States joined NATO under President Harry Truman in 1949.)

Mr. Biden’s campaign described the ad as a “six-figure” push but declined to say exactly how much it was spending. It said the ad would run in a variety of forms on Meta, Google, Yahoo Native and YouTube.