Powell left the door open to further rate cuts and said the end of the Fed's effort to shrink its holdings may be coming into view.

(Reuters) -- Wall Street ended mixed on Tuesday as investors digested mostly positive quarterly results from big U.S. banks, comments from Federal Reserve Chair Jerome Powell and an ongoing U.S.-China trade war.

US sanctions are intended to make it practically impossible to pay Iran for oil. But China, Iran's biggest buyer, has evaded the controls with a solution involving a workaround that allows billions of dollars' worth of crude purchases to continue to flow.