U.S. Democratic Senator Elizabeth Warren Wednesday pressed top Federal Reserve official and former veteran Wall Street bank attorney Randall Guynn to explain how he is handling potential conflicts of interest in his new role, according to a letter reviewed by Reuters.

Reuters was first to report last month that Guynn, who had worked for the biggest U.S. banks during his 40-year career at Davis Polk, has been tapped for a powerful Fed position policing the industry, reporting to Fed Vice Chair for Supervision Michelle Bowman.

The supervision and regulation division is responsible for the Fed's broad oversight of the banking sector, which includes setting rules for and examining the nation's largest, most complex financial institutions.

A Fed spokesperson confirmed receipt of the letter, but declined to comment further.