President Donald Trump’s nominee to chair the Federal Reserve says that he never promised the White House he would cut interest rates, even as the president renewed his calls for the central bank to do so. The comments underscore the challenge faced by Kevin Warsh, 56, a former top Fed official whom Trump named in January to replace the current Fed chair, Jerome Powell. Democrats on the committee accused Warsh on Tuesday of flip-flopping on interest rates over the years, supporting higher interest rates under Democratic presidents and advocating rate cuts during Trump’s time in office.