President Donald Trump early on Monday said he would call for an investigation into musician Bruce Springsteen’s endorsement of former Vice President Kamala Harris’ presidential run.

“I am going to call for a major investigation into this matter,” Trump said in a post on his Truth Social network. “Candidates aren’t allowed to pay for ENDORSEMENTS, which is what Kamala did, under the guise of paying for entertainment.”

Springsteen preformed at Harris’ campaign appearance in Georgia in October. Trump in his Monday post asked how much Harris had paid the musician.

His call for a probe followed a back-and-forth between the president and the songwriter last week.

As he took the stage in Manchester, England, last Wednesday, Springsteen had called “upon the righteous power of art, of music, of rock and roll, in dangerous times.”

“In my home, the America I love, the America I’ve written about, that has been a beacon of hope and liberty for 250 years is currently in the hands of a corrupt, incompetent, and treasonous administration,” Springsteen said.

He added, “Tonight we ask all who believe in democracy and the best of our American experiment to rise with us, raise your voices against authoritarianism and let freedom ring!”

Trump in a subsequent post on Truth Social called Springsteen “overrated” and said he shouldn’t speak about America “until he gets back into the Country.”