March 21 (Reuters) - ICE cotton futures hit a more than two-week low on Tuesday, weighed down by weakness in the grains market.

The May cotton contract on ICE Futures U.S. hit a session low of 76.68 cents a lb, a bottom since March 3.

"Grain prices are down a little... acreage estimates continue to increase for new (cotton) crop and (export) sales this week are not expected to be as high as last week," said Rogers Varner, president of Varner Brokerage in Cleveland, Mississippi.

The weekly U.S. export sales data will be released by the U.S. Department of Agriculture on Thursday.

U.S. wheat futures dropped to their lowest level in more than six weeks on Tuesday, corn futures hit a one-week low, while declines in soybeans were limited by bargain buying.

* The May cotton contract on ICE Futures U.S. settled down 0.49 cent, or 0.63 percent, at 76.84 cents per lb. It traded within a range of 76.68 and 77.48 cents a lb.
* Total futures market volume rose by 9,166 to 31,548 lots. Data showed total open interest fell 965 to 280,740 contracts in the previous session.
* The Thomson Reuters CoreCommodity CRB Index , which tracks 19 commodities, was down 0.27 percent.

(Reporting by Karen Rodrigues in Bengaluru; Editing by Leslie Adler)