* Indexes off: Dow 0.18 pct, S&P 0.4 pct, Nasdaq 0.59 pct
By Chuck Mikolajczak
NEW YORK, Sept 22 (Reuters) - U.S. stocks were trading lower on Monday after China's finance minister indicated the country will not increase stimulus measures and housing data fell short of expectations.
China will not dramatically alter its economic policy because of any one economic indicator, Finance Minister Lou Jiwei said on Sunday, days after many economists lowered growth forecasts having seen the latest set of weak data.
"With China's statements not defining clear hurdles for stimulus, the market is grappling to guess which data point will tip the hand that controls the purse strings," said Andre Bakhos, managing director at Janlyn Capital LLC in Bernardsville, New Jersey.
The National Association of Realtors said U.S. existing home sales dropped 1.8 percent to an annual rate of 5.05 million units, following four straight months of gains. Expectations called for sales increasing to a 5.20 million-unit pace.
The Dow Jones industrial average was falling 31.82 points, or 0.18 percent, to 17,247.92, the S&P 500 was losing 8.02 points, or 0.4 percent, to 2,002.38 and the Nasdaq Composite was dropping 27.07 points, or 0.59 percent, to 4,552.72.
Sigma-Aldrich shares were up 34 percent to $137.13 as the best performer on the S&P 500 after German drugs and chemicals maker Merck KGaA agreed to acquire Sigma-Aldrich for $17 billion in cash to boost its life science business.
Yahoo shares were trading down 3.6 percent to $39.44. The stock was downgraded by Bank of America Merrill Lynch and by Bernstein in the wake of the Alibaba Group debut Friday. Alibaba shares were down 3.2 percent to $90.90.
Dresser-Rand shares were up 2.6 percent to $82 after Germany's Siemens agreed to buy Dresser-Rand, a U.S. oilfield equipment maker, for $7.6 billion in cash. The stock had rallied more than 17 percent last week in anticipation of the deal.
Among the largest percentage gainers on the New York Stock Exchange was Kemet, up 12.4 percent after its second-quarter outlook, while the largest percentage decliner was CARBO Ceramics, down 17.86 percent.
Among the most active stocks on the NYSE were Alibaba , Bank Of America, up 1.12 percent to $17.14 and Vale SA ADR, down 3.50 percent to $11.58.
On the Nasdaq, Yahoo, Chinanet Online, up 76.3 percent to $3.46, and Apple, up 0.4 percent to $101.34 were among the most actively traded.
Declining issues were outnumbering advancing ones on the NYSE by 2,256 to 580, for a 3.89-to-1 ratio on the downside; on the Nasdaq, 1,880 issues were falling and 630 advancing for a 2.98-to-1 ratio favoring decliners.
The benchmark S&P 500 index was posting 10 new 52-week highs and 9 new lows; the Nasdaq Composite was recording 20 new highs and 69 new lows. (Reporting by Chuck Mikolajczak; Editing by Chizu Nomiyama and Nick Zieminski)