President Trump has called Michael D. Cohen a “rat” and a “liar.” Mr. Cohen, the president’s former personal lawyer and fixer, has likened Mr. Trump to a mobster.

Now they are poised to formally — and publicly — bury the hatchet.

Mr. Trump is expected to call into a radio show Mr. Cohen is hosting on Thursday, capping one of the more stunning rapprochements of the Trump era.

The conversation, scheduled to air on a Trump-friendly station in New York, WABC, comes nearly eight years to the day that Mr. Cohen pleaded guilty to federal crimes and implicated Mr. Trump in the same wrongdoing.

It also comes more than two years after Mr. Cohen served as the star witness at Mr. Trump’s criminal trial in New York State Court, delivering testimony that helped secure the then-former president’s conviction for falsifying business records related to a hush-money deal with a porn star.

Their planned radio appearance was first reported by MS NOW.

The White House did not immediately respond to a request for comment.

In a text message on Wednesday, Mr. Cohen said that Mr. Trump would call into WABC on Thursday, and that their conversation would air at 6 p.m.

It will mark their first public appearance together since their relationship crumbled during Mr. Trump’s first term. They met briefly last year at the president’s private, members-only golf club in Bedminster, N.J., breaking a yearslong estrangement, The New York Times reported.

More recently, as Mr. Cohen sought to make peace with his former boss, he renounced his cooperation with the prosecutors who brought charges against Mr. Trump.

Mr. Cohen, who once vowed to help prosecutors hold Mr. Trump “accountable for his dirty deeds,” now contends that he “felt compelled and coerced to deliver what they were seeking.” He also accused prosecutors of posing “inappropriate leading questions to elicit answers that supported their narrative.”

After issuing that criticism in January, Mr. Cohen met with Mr. Trump in Florida. By the summer, with the White House’s apparent blessing, Mr. Cohen debuted a radio show on WABC. He said Mr. Trump would eventually join him as a guest.

It is unclear what they will discuss on air on Thursday, but in a text message on Wednesday, Mr. Cohen promoted it like a prime-time exclusive.

“Two old friends separated by time, betrayal, and the world’s biggest spotlight…sit down, face to face,” Mr. Cohen wrote. “It’s time to talk.”

Shawn McCreesh contributed reporting.