UPDATE 1-GSI Commerce posts wider Q3 loss, shares fall

* Q3 loss/shr $0.28 vs est loss/shr $0.24

* Revenue $284.1 mln vs est $281.6 mln

* Sees FY 2010 rev $1.35 bln, in line with est

* Shares fall 7 pct in after-mkt trade

Oct 27 (Reuters) - Retail website operator GSI Commerce Inc GSIC.O posted a wider-than-expected quarterly loss, hurt by higher operating expenses, sending its shares down 7 percent in extended trade.

GSI Commerce, which competes with Amazon.com Inc (AMZN.O) and Art Technology Group Inc ARTG.O in the e-commerce business, expects full-year revenue of $1.35 billion, in line with analysts' estimates.

For the third quarter, GSI Commerce's net loss widened to $18.6 million, or 28 cents a share, from a loss of $9.4 million, or 18 cents a share, in the year-ago period.

Revenue rose 49 percent to $284.1 million.

Analysts on average expected a loss of 26 cents a share, on revenue of $281.6 million, according to Thomson Reuters I/B/E/S.

Total costs and expenses for the quarter rose about 52 percent to $304.4 million.

GSI Commerce shares were down at $23.50 in extended trade, after closing at $25.35 Wednesday on Nasdaq. They have fallen 5 percent since the company posted second-quarter results on July 28. (Reporting by Siddharth Cavale in Bangalore; Editing by Anne Pallivathuckal)