NEW YORK (AFP) - US stocks on Wednesday opened mostly lower as investors await the latest policy announcement from the US Federal Reserve later in the day.

Five minutes into trade, the Dow Jones Industrial Average dipped 20.53 (0.13 per cent) to 15,297.70.

The broad-based S&P 500 slipped 2.06 (0.12 per cent) to 1,649.75, while the tech-rich Nasdaq Composite Index was up a scant 0.32 (0.01 per cent) at 3,482.30.

Investors have been skittish about the Fed's intentions in recent weeks after Fed officials signaled they would begin to consider scaling back a stimulus programme that involves buying US$85 billion (S$105.93 billion) a month in bonds.

But in recent days, the market has become more confident that Federal Reserve Chairman Ben Bernanke would reassure markets that the bond-buying programme would remain in place for some time because the economic recovery is still not strong enough.

"The stock market's confidence in getting what it wants is evident in the 1.5 per cent gain registered by the S&P 500 this week," wrote Briefing.com analyst Patrick O'Hare.

"Accordingly, it could get ugly if the FOMC and Fed Chairman Bernanke don't live up to the market's bullish expectations."