Shares were set to fall on Wednesday, giving up some of the hefty gains of the previous session, which were based on hopes that Federal Reserve chairman Ben Bernanke will announce measures to stimulate the struggling U.S. economy

At 4:47 a.m. EDT, futures for the S&P 500 Dow Jones and Nasdaq 100 were down between 0.7 and 0.8 percent.

Bernanke speaks to a central bank conference on Friday in Jackson Hole, Wyoming. Analysts and commentators are divided on how much scope he has to announce further stimulus measures.

The FTSEurofirst 300 <.FTEU3> index of leading European shares was up 0.3 percent at 927.00 points.

Heineken NV , the world's third largest brewer, fell 12.3 percent after first-half profit came in below forecasts and it said volumes in Europe and the United States would suffer from economic uncertainty.

The Nikkei stock average <.N225> fell 1.1 percent on Wednesday as Moody's Investors Service's downgrade of Japan's sovereign debt rating spurred investors to take profits, erasing intraday gains made on speculation of more U.S. easing.

Orders for cars and planes probably helped U.S. durable goods orders rebound. After a disappointingly weak June, orders likely rose 2.0 percent, reversing the prior month's 1.9 percent decline. Data for July is due at 8:30 a.m. EDT.

Quarterly profit at Applied Materials is expected to increase to 33 cents per share, 4 cents per share better than the same period one year ago. The chip-manufacturing equipment maker last month said tough economic conditions in Europe and the United States were hurting demand.

U.S. stocks shot higher on Tuesday on speculation Bernanke this week would signal new help for the economy, giving investors hope a four-week rout was nearing an end. Weak data in housing and regional factory activity triggered the latest round of bets that Bernanke will act, even though the Fed's options appear limited.

The Dow Jones industrial average <.DJI> rose 3 percent; the Standard & Poor's 500 Index <.SPX> rose 3.4 percent; the Nasdaq Composite Index <.IXIC> rose 4.3 percent.

A strong earthquake rattled the U.S. East Coast on Tuesday, sending tremors as far as Canada, damaging well-known buildings in the nation's capital and sending scared office workers into the streets.

(Reporting by Brian Gorman; Editing by Hans-Juergen Peters)