Stocks were set for a slightly lower open on Wednesday after data showed orders for durable goods unexpectedly fell in June and Boeing Co's 2010 profit outlook was beneath Wall Street's consensus forecast.

New orders for long-lasting U.S. manufactured goods posted their largest decline since August, according to a government report, unexpectedly falling for a second month running. The data confirmed economic growth wilted in the second quarter.

It puts us in line for more of the trading-range market today, said Alan Lancz, president of Alan B. Lancz & Associates Inc in Toledo, Ohio.

S&P 500 futures were unable to move past their 200-day simple moving average, which is proving to be a strong resistance level. The S&P 500 Index <.SPX> closed above its 200-day SMA on Monday for the first time in a month but failed to confirm that close in the next session.

Earnings have been good, guidance has been good, but once earnings season is over, it's going to prove difficult to sustain those levels even if we do break them, Lancz said.

Boeing reported a higher-than-expected quarterly profit but forecast full-year earnings slightly below Wall Street's consensus estimate, and its shares fell 1.2 percent to $67.80 in premarket trading.

S&P 500 futures fell 2.3 points and were slightly below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures dropped 31 points and Nasdaq 100 futures shed 3.5 points.

The S&P 500 snapped a three-day winning streak on Tuesday after mixed earnings reports and a fall in consumer confidence. The Dow Jones industrial average added 0.1 percent while the Nasdaq was off 0.4 percent.

Sprint Nextel shares rose 4.8 percent to $5.06 in premarket trading after it posted results and said it had lost fewer monthly contract customers in the second quarter than analysts had expected.

ConocoPhillips , the third-largest U.S. oil company, reported a better-than expected quarterly profit and said it will sell its entire stake in Lukoil. The shares rose 1.8 percent in premarket trades.

Defense contractor General Dynamics Corp posted a better-than-expected quarterly profit, though its revenue came in slightly below Wall Street's forecast. Its shares fell 1.6 percent to $60.80.

(Additional reporting by Matthew Lynley; Editing by Padraic Cassidy)