* S&P 500 falls below 1,900 for first time since early Oct
* Amazon biggest drag on S&P 500, Nasdaq
* Indexes down: Dow 2 pct, S&P 2.2 pct, Nasdaq 2.9 pct (Updates to late afternoon)
By Caroline Valetkevitch
Jan 13 (Reuters) - U.S. stocks sold off sharply in late Wednesday trading, pushing the S&P 500 below 1,900 for the first time since early October, after the market failed to hold its early rally.
All 10 S&P 500 sectors were in the red and extending losses in afternoon trading. Decliners outpaced advancing issues on the NYSE by a ratio of 7.53-to-1 and by 6.44-to-1 on the Nasdaq.
The S&P 500 is now down more than 11 percent from its May 20 lifetime high, while the Russell 2000 dropped 3.5 percent and was on pace to end the session in bear market territory.
Analysts noted a trend in stocks selling off significantly once a rally has faded.
"Thus far in the new year, buyers have waited until late in the day and created sharp late day rallies. These rallies have prevented the market form settling on its lows," said Michael O'Rourke, chief market strategist at JonesTrading in Greenwich, Connecticut.
"Thus we have yet to reach the capitulation point and the new buyers are caught every day. This is the most bearish way for the market to sell off."
A brief rally in beaten-down oil prices stalled, also dragging down U.S. stocks.
At 2:55 p.m., the Dow Jones industrial average was down 324.81 points, or 1.97 percent, to 16,191.41, the S&P 500 had lost 42.41 points, or 2.19 percent, to 1,896.27 and the Nasdaq Composite had dropped 137.16 points, or 2.93 percent, to 4,548.76.
Amazon fell 4.9 percent to $587.18 and was the biggest drag on the S&P 500 and the Nasdaq.
CSX was down 6.8 percent at $22.10 after the railroad company's fourth-quarter profit fell on declining freight volumes.
The S&P 500 posted 2 new 52-week highs and 103 new lows; the Nasdaq recorded 7 new highs and 456 new lows. (Additional reporting by Abhiram Nandakumar in Bengaluru; Editing by Savio D'Souza and Chizu Nomiyama)