This week's set-piece event is the Jackson Hole central-bank gathering in Wyoming, slated for Thursday through Saturday. Investors will be glued to Federal Reserve Chair Jerome Powell's speech, hoping for any insight into whether the central bank might kick off interest-rate cuts in September.

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 symposium later this week for clues on the monetary policy path.

The Nasdaq fell as megacaps lost, after having rallied for much of the year. Nvidia fell 3.5%, the biggest drop in nearly four months.