Sen. Bernie Sanders (I-Vt.) dinged Donald Trump at a Labor Day event on Monday, saying the president was working “night and day ― on behalf of his fellow billionaires.”

Sanders also called Trump a “pathological liar” and accused him of dividing America for “cheap political reasons.”

We “have a president who is not doing what almost every president in American history has done — when you make it into the Oval Office, you understand you’ve got a sacred responsibility to bring the American people together,” said Sanders per The New Hampshire Union Leader.

Sanders’ sharp criticism at an AFL-CIO breakfast in Manchester, New Hampshire, came amid restive rumblings between Trump and the nation’s largest federation of unions.

On Sunday, AFL-CIO president Richard Trumka told Fox News Sunday that the president was hurting American workers and that his members would “probably” be voting for Democratic candidates in the midterm elections.

While unemployment might be down, so are wages, Trumka said. Despite Trump’s promises that massive corporate tax cuts would boost wage growth, pay only increased modestly, and any increases were swamped by growing inflation.

“So overall, workers aren’t doing as well,” said Trumka, who represents 12.5 million workers. He also accused the Trump administration of scuttling health and safety regulations that will “hurt us on the job.”

After Trumka’s appearance on Fox News Sunday, Trump blasted the union leader on Twitter:

Richard Trumka, the head of the AFL-CIO, represented his union poorly on television this weekend. Some of the things he said were so against the working men and women of our country, and the success of the U.S. itself, that it is easy to see why unions are doing so poorly. A Dem! — Donald J. Trump (@realDonaldTrump) September 3, 2018

While there was no direct AFL-CIO response to Trump’s tweet, Trumka made a statement on CNN that said working people were “demanding nothing more — and certainly nothing less — than our fair share of the immense wealth we create every day.”

📺WATCH / RT: On this #LaborDay, we are headed forward without one thing, that is fear. America is hungry for unity. Unions are leading our country forward. #1u pic.twitter.com/LMvYq6cwko — AFL-CIO (@AFLCIO) September 3, 2018