The S&P 500 struggled to break a key technical level as conflicting reports showing improved corporate earnings and falling orders for the most expensive manufactured goods kept U.S. stocks slightly lower on Wednesday.

The Standard & Poor's 500 index has failed to gain any significant ground. It fell on Tuesday after a three-day rally up to its 200-day moving average, a closely watched measure of market direction.

Earnings have gotten us up to this point, but there has to be some sort of good catalyst to push (the S&P) through the 200-day moving average on a sustainable basis, said Scott Wren, senior equity strategist at Wells Fargo Advisors in St. Louis.

The S&P's 200-day moving average is currently around 1,114. Investors are struggling to either define it as the top of a recent rally or a consolidation point leading to further gains.

Boeing Co reported a higher-than-expected quarterly profit but forecast full-year earnings slightly below Wall Street's estimate. The plane maker's shares fell 1.5 percent to $67.62.

With 49 percent of the S&P 500 having reported earnings, 77 percent of companies have beat expectations, according to Thomson Reuters Proprietary Research.

The Dow Jones industrial average <.DJI> dropped 13.70 points, or 0.13 percent, to 10,523.99. The Standard & Poor's 500 Index <.SPX> dropped 3.95 points, or 0.35 percent, to 1,109.89. The Nasdaq Composite Index <.IXIC> dropped 12.92 points, or 0.56 percent, to 2,275.33

New orders for long-lasting U.S. manufactured goods unexpectedly fell for a second straight month in June, posting their largest decline since August.

Most of that durable goods report wasn't bad. The aircraft portion of that is always very volatile, Wren said. Without aircraft orders and focusing on nondefense, it was somewhat positive and took some of the edge off.

Defense contractor General Dynamics Corp and ConocoPhillips , the third-largest U.S. oil company, both posted stronger-than-expected quarterly profits. General Dynamics shares rose 0.2 percent to $61.89, and ConocoPhillips shares were up 0.3 percent to $54.60.

The S&P energy sector <.GSPE> edged higher, up 0.15 percent.

(Reporting by Matthew Lynley; Editing by Kenneth Barry)