President-elect Joseph R. Biden Jr on Thursday defended his son, Hunter Biden, who is under federal investigation for tax fraud, saying that accusations of wrongdoing against him were “kind of foul play”.

“I’m not concerned about any accusations that have been made against him. It’s used to get to me,” Biden said in an interview with late-night talk show host Stephen Colbert.

“I think it’s kind of foul play,” Biden said in a clip of the interview that CBS released on Thursday afternoon, several hours before it was scheduled to air on the Late Show with Stephen Colbert. He added, “It is what it is.”

Last week Hunter Biden disclosed that the US attorney’s office in Delaware is investigating him for tax fraud. The two-year investigation began as an inquiry into potential money laundering crimes, according to multiple federal officials familiar with the investigation. FBI agents were unable to gather enough evidence to move forward with the money laundering aspect of the case, they said.

“I am confident that a professional and objective review of these matters will demonstrate that I handled my affairs legally and appropriately, including with the benefit of professional tax advisers,” the younger Biden said.