The United Auto Workers union says it has filed labor charges against former US President Donald Trump and billionaire entrepreneur Elon Musk for their illegal attempts to threaten and intimidate workers in an interview.

The UAW took issue with remarks made in Trump's interview on Monday with Musk on the social media platform X.

Trump called Musk "the greatest" for his handling of workers who went on strike.

Trump said to Musk, "I look at what you do." He went on to say, "they go on strike and you say, That's OK, you're all gone."

The UAW released a statement on Tuesday. It noted that under federal law, workers cannot be fired for going on strike, and threatening to do so is illegal.

The UAW said Trump and Musk advocated for the illegal firing of striking workers. The union said it had filed charges against the "disgraced billionaires" for their illegal attempts to threaten and intimidate workers.

US media outlets say the National Labor Relations Board has accepted the UAW's complaints.

The UAW has endorsed Vice President Kamala Harris, for the US presidential election in November.

A Trump campaign senior advisor has told US media that the "frivolous lawsuit is a shameless political stunt intended to erode President Trump's overwhelming support among America's workers."