Wall Street's main indexes fell on Monday after U.S. President Donald Trump rekindled worries about the fallout of a global trade war by introducing new tariffs, while focus remained on the Federal Reserve's monetary policy decision later this week.

Trump announced a 100% tariff on movies produced outside the U.S. but offered little clarity on how the levies would be implemented. Movie and television production companies that film overseas fell in premarket trading.

U.S. stock index futures fell on Monday after President Donald Trump reignited concerns about the effects of a global trade war by introducing new tariffs, while markets awaited the Federal Reserve's monetary policy decision this week.