President Donald Trump on Thursday signaled his continued support for a Department of Justice investigation into Federal Reserve Chairman Jerome Powell — a stance that could further delay the confirmation of Powell’s would-be successor, Kevin Warsh.

“He’s under investigation because he’s building a building for hundreds of billions of dollars more than it’s supposed to cost,” Trump said of Powell in the Oval Office.

He was referring to the ongoing renovation of the Fed’s headquarters and another building in Washington, the purported focus of the federal criminal probe of the central bank chairman led by U.S. Attorney Jeanine Pirro. Trump repeatedly claimed that the construction projects cost up to $4 billion, though the actual total is roughly $2.5 billion.

Powell has accused the government of launching the investigation in retaliation for his refusal to lower interest rates as much or as quickly as Trump has demanded.

Powell “should be lowering rates immediately,” Trump said unprompted in his Oval Office remarks, “but he won’t do that because he’s he’s a stubborn, incompetent person, and that’s a bad thing.” Trump spoke to reporters as he sat next to Japanese Prime Minister Sanae Takaichi before a bilateral meeting.