An emerging rift between Melania Trump and Hunter Biden escalated Thursday when the son of former President Joe Biden issued an expletive-laden response to the first lady’s demand that he apologize for an allegation he made about her alleged prior ties to convicted sex trafficker Jeffrey Epstein.

Last month, during an interview with YouTube host Andrew Callaghan, Hunter Biden said it was Epstein, the wealthy financier and convicted sex offender who died by suicide in jail in 2019, who initially introduced Melania Trump to her future husband, President Donald Trump — an assertion that Alejandro Brito, an attorney for Melania Trump, called untrue and “extremely salacious” in a letter to Hunter Biden last week.

Brito’s letter to Hunter Biden, a copy of which was reviewed by ABC News, threatened a billion-dollar lawsuit if he failed to retract the claim, which Brito said caused Melania Trump “overwhelming financial and reputational harm.”

On Thursday, Hunter Biden reappeared on Callaghan’s YouTube program, where he was offered an opportunity to apologize to Melania Trump.

“F— that, that’s not going to happen,” he shot back.

“[Epstein and Trump] knew each other well, they spent an enormous amount of time together,” Hunter Biden said, citing an excerpt from a book written by Michael Wolff, a Trump biographer, to back up his claim.

President Trump has criticized Wolff as a “third rate reporter” and questioned many of Wolff’s anecdotes about him and his family.

Former first lady Melania Trump looks on during an election night event for Republican presidential nominee, former President Donald Trump at the Palm Beach Convention Center, Nov. 6, 2024, in West Palm Beach, Fla. Hunter Biden, son of President Joe Biden departs the J. Caleb Boggs Federal Building, June 3, 2024, in Wilmington, Del.
Chip Somodevilla/Getty Images | Anna Moneymaker/Getty Images

The Daily Beast, which also reported on Wolff’s claim, took down their story on the matter after receiving a similar letter from Melania Trump’s lawyer, and issued an apology “for any confusion or misunderstanding.”

“I only can go by what people are saying, I don’t know,” Hunter Biden told Callaghan.

“If they want to sit down for a deposition and clarify the nature of the relationship between Jeffrey Epstein — if the president and the first lady want to do that … I’m more than happy to provide them the platform to be able to do it,” he said.

Asked to respond to Hunter Biden’s comments, Nick Clemens, a spokesperson for Melania Trump, told ABC News, “First Lady Melania Trump’s attorneys are actively ensuring immediate retractions and apologies by those who spread malicious, defamatory falsehoods. The true account of how the First Lady met President Trump is in her best-selling book, ‘Melania.’”

In her memoir, Melania Trump said she and Trump met at a 1998 Fashion Week party in New York, and that the two were introduced by a modeling agent.

Hunter Biden is no stranger to legal wrangling. Weeks ahead of Trump’s inauguration, then-President Biden pardoned his son shortly before two federal judges were scheduled to sentence him for a pair of criminal convictions in Delaware and California, for which he faced the possibility of substantial prison time.

He also filed a flurry of lawsuits against individuals who he accused of peddling and misusing the contents of his laptop shortly before the 2020 presidential election. One of those suits, which targeted former Overstock.com CEO Patrick Byrne for alleged defamation, is scheduled to go to trial this fall.