* Dec/March spread widens ahead of Dec contract delivery
* March cotton reverses gains to finish down
* Harvest pressure pins futures near 10-month lows
NEW YORK, Nov 19 (Reuters) - Cotton futures ended little-changed on Tuesday in spread-related dealings ahead of the December contract's expiry and under harvest pressure.
The most-active March cotton contract on ICE Futures U.S. reversed earlier gains to close down 0.15 cent, or 0.2 percent, at 77.56 cents a lb, hovering near last week's ten-month low of 77.37 cents.
The spot December cotton contract on ICE Futures U.S. eased 0.49 cent, or 0.6 percent, to finish at 75.88 cents a lb, nearing its Dec. 6 expiry.
Cotton performed in line with broader commodities markets, as the Thomson Reuters/Core Commodity CRB index touched the lowest level in more than a year.
Exchange stocks continued their climb to the highest levels since July, with inventories totaling 208,471 bales on Monday, according to the most recent ICE data.
A weekly U.S. government crop report showed that harvesting has gathered pace in the world's top exporter, though it remains behind previous years.
Prices in No 2 producer India are expected to trade steady-to-lower this week, as new crop supplies come online and demand for exports slows.
The day's spread-related trade left the December contract at a discount of 1.68 cents a lb to the March contract , compared with 1.34 cents a lb previously.
"We've got commercial and trade rolling. Unless you want to be involved in the delivery process, you're rolling forward or getting out," said Keith Brown, president of commodity firm Keith Brown and Co. in Moultrie, Georgia.
"We've gotten more pressure coming in from harvest, and the path of least resistance for cotton is lower."
Prices have tumbled some 17 percent from August highs near 94 cents, teetering on the edge of a bear market as speculators have switched to a net short stance from a big bullish position.
Dealers eyed news on China's reserve auctions, expected to begin this week. The sales stand to pressure global prices, as Beijing looks to offload some of its huge inventories.
Beijing's purchasing has slowed ahead of the anticipated sales, as the government raises quality standards and considers a larger revamp of the stockpiling program launched in 2011. (Reporting by Chris Prentice; Editing by Krista Hughes)