Nov 21 (Reuters) -ICE cotton futures fell nearly 1% on Tuesday on lingering demand concerns and a good harvest season offsetting support from a weaker U.S. dollar on the natural fiber market.

* The second-month March contract CTc2 was down 0.76 cent, or 0.9%, at 80.49 cents per lb at 12:09 ET (1709 GMT).

* The dollar index fell for a third straight session on Tuesday, hitting its lowest in about 2-1/2 months and making cotton less expensive for overseas buyers. USD/

* "Low demand for actual downstream textiles, yarn stocks steadily rising and the operating rates of all spinners in almost all locations falling are pressuring cotton prices," said Louis Barbera, partner and analyst at VLM Commodities.

* "Weather has been absolutely perfect for harvest for the second year in a row and that does not make for a smaller crop... we're seeing it right now with the upward revision of the U.S. crop to which we think there will be a slight upward revision again in the coming weeks," Barbera said.

* Around 77% of the U.S. cotton crop had been harvested as of the week ended Nov. 19, compared with 67% in the prior week, according to the U.S. Department of Agriculture's weekly crop progress report. US/COT

* Oil fell as investors turned cautious ahead of a meeting of OPEC+ this Sunday when the producer group may discuss deepening supply cuts.

* Lower oil prices make polyester, a substitute for cotton, less expensive. O/R

* In the grain market, U.S. soybean futures gained more ground as the market remained concerned about parched conditions in Brazil despite some rain relief at the weekend. Chicago corn and wheat inched up.GRA/

Reporting by Sherin Elizabeth Varghese in Bengaluru; Editing by Shailesh Kuber