GOP senator vows to block Trump's Fed chair pick unless Powell probe is dropped

"Kevin Warsh is a qualified nominee with a deep understanding of monetary policy," Tillis wrote. "However, the Department of Justice continues to pursue a criminal investigation into Chairman Jerome Powell based on committee testimony that no reasonable person could construe as possessing criminal intent."

"I will oppose the confirmation of any Federal Reserve nominee, including for the position of Chairman, until the DOJ's inquiry into Chairman Powell is fully and transparently resolved."

Trump has repeatedly called for such a change and Powell has resisted so far, citing a need for the agency to protect its independent operations.

"Look, there are lots of federal buildings being built. Trump doesn't have an opinion on how efficiently they're being built. Nobody believes that this is about testimony before the Senate committee," Sherman said earlier in January when the DOJ announced its investigation.

"It's simply outrageous," he added.

"Protecting the independence of the Federal Reserve from political interference or legal intimidation is non-negotiable. My position has not changed," Tillis said.