Wall Street will be listening closely to Federal Reserve Chair Jerome Powell's speech Friday at the Jackson Hole economic policy summit, where he could signal whether the central bank is ready to cut borrowing costs at its next meeting in September.

The Justice Department signaled possible plans to investigate Federal Reserve Governor Lisa Cook, with a top official informing Federal Reserve Chair Jerome Powell of the probe and encouraging him to remove her from the board in a letter sent Thursday.

President Donald Trump is calling on a Federal Reserve governor to resign over an accusation of mortgage fraud.

The U.S. dollar drifted on Thursday as investors fretted about the Federal Reserve's independence after yet another attack from President Donald Trump ahead of remarks from Chair Jerome Powell later this week that could influence the outlook for rates.