July 18 (Reuters) -ICE cotton futures edged lower on Thursday, hurt by a stronger dollar, lower weekly exports of the natural fiber and weakness in grains market.

* Cotton contracts for December CTZ4 fell 0.28 cents, or 0.39%, to 71.79 cents per lb at 1619 GMT.

* "Cotton has been trading on both sides of unchanged, with modest negative bias on a higher dollar and most of the U.S. agricultural space," said Valentin Olah, risk management consultant at StoneX Group.

* The dollar index .DXY was up 0.3% against its rivals after dropping to a near four-month low in the previous session, making the natural fiber more expensive for overseas buyers. USD/

* Chicago soybean futures hit their lowest level in nearly four years on Thursday under pressure from favourable crop weather in the U.S. Midwest while wheat rose slightly, buoyed by strong demand. GRA/

* Meanwhile, the U.S. Department of Agriculture (USDA) showed export sales of 113,100 running bales (RB) were down 30% from the previous week and 33% from the prior 4-week average. EXP/COT

* The report also showed net sales of Upland cotton totaling 27,200 RB for 2023/2024, a marketing-year low, were down 50% from the previous week.

* The Nasdaq and the S&P 500 bounced back on Thursday, boosted by a recovery in megacaps. .N

Reporting by Anushree Mukherjee and Anmol Choubey in Bengaluru; Editing by Devika Syamnath