The president's latest attack comes as Powell is scheduled to deliver remarks at the Fed's annual conference in Jackson Hole, WY, on Friday.

Gold prices edged lower on Tuesday as the U.S. dollar firmed, while investors hunkered down for Federal Reserve Chair Jerome Powell's speech at Jackson Hole later this week.

Stocks start the week just shy of record highs, underpinned by a well-received corporate earnings season and hopes the Federal Reserve will soon start reducing official borrowing costs again. Investors are therefore keen that Friday’s keynote address by Fed Chair Jerome Powell at the Jackson Hole symposium will be suitably dovish.

At the end of the week, investors look forward to Powell's speech at the annual Jackson Hole Economic Symposium.

The U.S. dollar was little changed on Wednesday as traders awaited a speech from Federal Reserve Chair Jerome Powell at the annual Jackson Hole central bankers' symposium later this week for clues on the path of monetary policy.