US stock futures remained flat as investors braced themselves for the release of the Federal Reserve's next policy decision amid a volatile trading week.

So far, the Federal Reserve has avoided commenting on the increasingly uncertain outlook, but investors are waiting to see whether it changes its projections on Wednesday.

U.S. stocks are drifting higher Wednesday as Wall Street waits to hear what the Federal Reserve will say in the afternoon about where interest rates may be heading. The S&P 500 was up 0.3% in early trading.