Feb 20 (Reuters) - U.S. cotton futures fell for a second straight session on Thursday, ahead of the release of government export data that traders say could indicate falling demand for the fiber.

The U.S. Department of Agriculture will release a weekly tally for domestic cotton shipments on Friday, with traders expecting a figure of around 100,000 running bales for the 2013/14 crop, versus the previous week's exports of 120,300.

"It's almost certainly going to be lower. That's the market's consensus, and that's probably why cotton's been priced down again today," said Sharon Johnson, senior cotton analyst at KCG Futures in Roswell, Georgia.

The most-active May cotton contract on ICE Futures U.S. settled down 0.26 cent, or 0.3 percent, at 87.65 cents a lb.

The spot March contract closed down 0.60 cent, or 0.7 percent, at 86.37 cents a lb as it headed toward its March 7 expiry.

On Wednesday, May lost 1.8 percent and March 1.1 percent.

Inventories of U.S. cotton have also crept up lately, weighing on sentiment.

Certified stocks ticked up to 250,606 bales, up from about 34,100 bales at the start of the year and the highest level since July, exchange data compiled by Reuters showed. (Reporting by Barani Krishnan; Editing by Lisa Shumaker )