* U.S. weekly exports sales fall 21 pct from previous week

* Prices reverse after buy stops lift them to session highs

* Reuters poll: U.S. farmers to boost cotton acres

* Brazil's Conab maintains outlook for higher 2013/14 output

NEW YORK, Jan 9 (Reuters) - ICE cotton futures fell on Thursday, under pressure from weak U.S. export sales data as high prices hurt demand and rebalancing of the most closely-followed commodities indexes.

The benchmark March cotton contract on ICE Futures U.S. closed down 0.33 cent, or 0.4 percent, at 82.81 cents a lb after dropping nearly 2 percent on Wednesday on fears the market was technically overbought.

The Thomson Reuters/Core Commodity CRB index, a benchmark for global commodities markets, tumbled to June 2012 lows as most of its 19 components fell.

U.S. weekly cotton export sales were down 21 percent from the previous week at 68,100 running bales in the week ended Jan. 2, showing that mill demand took a hit during the week prices climbed to the highest levels since October.

Shipment levels of previously-booked cotton picked up, however, the data showed.

Fiber was also under pressure as index funds cut their allocations in the commodity after prices climbed 13 percent last year.

"Mills don't like buying at these high levels," said Ron Lawson, managing director of logicadvisors.com.

"The industry is expecting the rebalancing to drive the market lower."

Even so, the spot price shot to an intraday high of 84.63 cents a lb as a climb to key levels triggered buy stops, dealers said.

A Reuters survey of traders, cooperatives, and industry experts showed that U.S. farmers were going to increase cotton acres for the first time in four years after cotton prices rallied and competing grains markets toppled from the previous year's highs.

Brazil's Conab on Thursday maintained expectations that farmers will boost cotton lint output by 25 percent to 1.63 million tonnes in 2013/14. (Reporting by Chris Prentice; Editing by Marguerita Choy)