US STOCKS-Wall St falls for 3rd day as earnings disappoint

* Dow in the red for the year

* Caterpillar (NYSE: CAT - news) falls after lower quarterly profit

* Indexes down: Dow 0.7 pct, S&P 0.6 pct, Nasdaq 0.4 pct (Updates to late afternoon)

By Caroline Valetkevitch

July 23 (Reuters) - Wall Street fell for the third straight day on Thursday following disappointing results and forecasts from companies including 3M and Caterpillar, adding to U.S. profit concerns.

The manufacturing companies' declines helped push the Dow Jones industrial average back into the red for the year. Also hurting the Dow was American Express, down 2.6 percent at $76.95 after revenue missed expectations.

Caterpillar shares fell 3.7 percent to $76.88 and hit a four-year low of $76.65. The world's largest construction and mining equipment maker reported sales declines in key markets in a sluggish global economy.

"Companies such as Caterpillar are a litmus test for the global economy, especially at a time when the market is concerned about China's economy," said Mark Luschini, chief investment strategist at Janney Montgomery Scott in Philadelphia.

Nine of the 10 major S&P 500 sectors were lower with the utilities index leading the decliners with a 1.8 percent fall.

The materials index fell 1.5 percent with Dow Chemical's 5.2 percent drop to $47.45 weighing the most on the sector. Dow Chemical warned of soft demand in China after posting stronger-than-expected results.

At 2:56 p.m., the Dow Jones industrial average fell 115.88 points, or 0.65 percent, to 17,735.16, the S&P 500 lost 11.58 points, or 0.55 percent, to 2,102.57 and the Nasdaq Composite dropped 22.30 points, or 0.43 percent, to 5,149.47.

3M was down 3.5 percent at $149.91 after the diversified manufacturer cut its full-year forecast.

While markets remain near record highs, second-quarter S&P 500 earnings have been mixed, with 75 percent of reports so far beating analysts' profit expectations and just 52 percent surpassing revenue expectations, according to Thomson Reuters (Dusseldorf: TOC.DU - news) data.

The S&P 500 is currently trading at 16.9 times forward 12 months earnings, above the 10-year median of 14.7 times, according to StarMine data.

Qualcomm (Swiss: QCOM.SW - news) fell 4.4 percent to $61.40, a day after the chipmaker said it may break itself up as it delivered its third profit warning this year.

On the plus side, SanDisk (NasdaqGS: SNDK - news) jumped 16.2 percent to $62.94, a day after the data storage products maker reported a quarterly profit that was double of what analysts had expected.

Declining issues outnumbered advancing ones on the NYSE by 2,094 to 934, for a 2.24-to-1 ratio on the downside; on the Nasdaq, 1,870 issues fell and 891 advanced for a 2.10-to-1 ratio favoring decliners.

The S&P 500 was posting 31 new 52-week highs and 39 new lows; the Nasdaq was recording 101 new highs and 125 new lows. (Additional reporting by Tanya Agrawal; editing by Don Sebastian and Nick Zieminski)