* Services sector expands at slowest rate since Feb -Markit
* ISM services short of expectations
* Factory orders fall for fourth straight month
* Indexes off: Dow 1.2 pct, S&P 1.3 pct, Nasdaq 1.7 pct (Updates to afternoon trading, changes byline)
By Caroline Valetkevitch
NEW YORK, Jan 6 (Reuters) - U.S. stocks were down more than 1 percent in afternoon trading on Tuesday, extending recent losses as data showed the pace of growth in the U.S. service sector had slowed and oil prices fell further.
Data on Tuesday pointed to slowing growth in the fourth quarter. The pace of expansion in services moderated in December and new orders for manufactured goods fell for a fourth consecutive month in November.
The S&P 500 fell below the 2,000 level for the first time since Dec. 17. On Monday, Wall Street had suffered its biggest drop since early October.
The S&P energy sector was down 1.8 percent and the biggest drag on the S&P 500. U.S. crude oil fell below $50 a barrel on mounting worries about a supply glut. U.S. crude was last down $1.85 at $48.19 after plumbing an April 2009 low at $47.74.
Among the day's biggest percentage decliners, shares of Southwestern Energy were down 4.5 percent. Brokerages continue to cut price targets on energy names.
Global "economic growth levels are questionable so ... the fear is portending a global slowdown," said Bucky Hellwig, senior vice president at BB&T Wealth Management in Birmingham, Alabama.
At 1:21 p.m., the Dow Jones industrial average fell 215.99 points, or 1.23 percent, to 17,285.66, the S&P 500 lost 25.7 points, or 1.27 percent, to 1,994.88 and the Nasdaq Composite dropped 78.80 points, or 1.69 percent, to 4,573.78.
An election in Greece, which may trigger its exit from the euro zone, is about three weeks away, increasing the difficulty for the European Central Bank to move towards quantitative easing as it attempts to stabilize the region's economy.
Declining issues outnumbered advancing ones on the NYSE by 2,240 to 806, for a 2.78-to-1 ratio on the downside; on the Nasdaq, 2,228 issues fell and 485 advanced for a 4.59-to-1 ratio favoring decliners. (Additional reporting by Rodrigo Campos; Editing by Chizu Nomiyama, Nick Zieminski and Meredith Mazzilli)