The Justice Department served the Federal Reserve with grand jury subpoenas on Friday, Fed Chair Jerome Powell said Sunday, threatening an “unprecedented” criminal indictment against him over cost overruns for the renovation of the Fed’s headquarters building.

Earlier Sunday, the New York Times reported the U.S. attorney’s office in the District of Columbia had opened an investigation into Powell over whether he lied to Congress over their scope of the renovations.

In a statement late Sunday, Powell said he has “deep respect” for the rule of law and accountability, but said questions about his testimony to Congress were “pretexts” and that the Trump administration’s action “should be seen in the broader context of the administration’s threats and ongoing pressure.”

“The threat of criminal charges is a consequence of the Federal Reserve setting interest rates based on our best assessment of what will serve the public, rather than following the preferences of the president,” Powell said.

“This is about whether the Fed will be able to continue to set interest rates based on evidence and economic conditions — or whether instead monetary policy will be directed by political pressure or intimidation.”

Sen. Thom Tillis, a North Carolina Republican who sits on Senate Banking Committee, decried the move.

“If there were any remaining doubt whether advisers within the Trump administration are actively pushing to end the independence of the Federal Reserve, there should now be none,” Tillis tweeted. “It is now the independence and credibility of the Department of Justice that are in question. I will oppose the confirmation of any nominee for the Fed — including the upcoming Fed Chair vacancy — until this legal matter is fully resolved.”

The Fed has historically maintained its independence from the White House, basing its monetary policies on data rather than ideology. Many worry that the Fed’s credibility would be undermined if the president could influence interest-rate decisions, among other things.

Over the past year, Trump has repeatedly pressured Powell and the Fed to cut interest rates, at times threatening to fire Powell, whose tenure as chairman ends in May. Trump has also sharply criticized the $2.5 billion renovation of the Fed’s main office building, claiming the project was mismanaged. In July, Trump said Powell should be investigated for deceptive testimony to Congress. Powell said at the time that the complaints were misleading and inaccurate.

The project, which began in 2017 and is expected to be completed in fall 2027, has run about $700 million above initial estimates. The Fed has said the cost overruns are due to part to unforeseen conditions like more asbestos than anticipated and a higher-than-expected water table.

“We do take seriously our responsibility as stewards of the public’s money,” Powell said at the time, according to Reuters, acknowledging that “the cost overruns are what they are.”

Trump has said he has already chosen Powell’s successor to lead the Fed, and that he will make his pick public this month. White House economic adviser Kevin Hassett and former Fed governor Kevin Warsh are believed to be the two top candidates.