(Reuters) - Wall Street's main indexes opened higher on Wednesday ahead of the Federal Reserve's widely anticipated monetary policy decision, at a time when worries about trade policies and their impact on the economy have rattled investors.

The Dow Jones Industrial Average rose 84.73 points, or 0.20%, to 41,666.04, the S&P 500 gained 18.29 points, or 0.33%, to 5,632.95, and the Nasdaq Composite gained 84.20 points, or 0.50%, to 17,588.32 at the opening bell.