* Good rains hit dry Argentina, Brazil farm belts
* USDA report seen cutting U.S. soy, corn supply estimates
* Argentina eases corn export ban, Russia eyes higher wheat tax (Rewrites throughout with U.S. market open, adds quote, updates prices, changes byline, changes dateline from PARIS/SINGAPORE)
CHICAGO, Jan 11 (Reuters) - U.S. soybean futures slipped from 6-1/2 year highs on Monday on crop-boosting rains in South America and as investors squared positions ahead of eagerly awaited U.S. government crop forecast data due on Tuesday.
Corn and wheat futures also pulled back from multi-year peaks posted last week as the U.S. dollar firmed and traders gauged good weekend rains in South America and looked ahead to the upcoming U.S. Department of Agriculture (USDA) reports.
Scheduled for release at 11:00 a.m. CST (1700 GMT) on Tuesday, the USDA reports are expected to show tightening supplies of key crops an may forecast higher demand from some major importers.
Grain markets have soared to the highest levels in years as rising global demand and hot, dry crop weather in South America reinforced concerns about tightening world supplies.
Recent rains in Argentina and Brazil exceeded expectations, triggering the market's retreat.
"Totalling up the rainfall amounts over the weekend and it looks like there are some higher than expected totals," said Brian Basting, analyst with Advance Trading. "One rain doesn't make a crop but it certainly takes an edge off the market going into tomorrow's reports."
Good export demand limited losses as the USDA on Monday confirmed new sales of 132,000 tonnes of soybeans to China and 108,500 tonnes of corn to Colombia.
Grain traders were also monitoring export curbs among key grain suppliers. Russia is considering raising its recently-imposed wheat export tax, while Argentina is backing off a corn export suspension announced last week.
Chicago Board of Trade March soybeans fell 4-1/2 cents to $13.70-1/4 a bushel by 12:45 p.m. CST (1845 GMT) after peaking at $13.88-3/4 earlier in the session, the highest price for a most-active contract since June 2014.
March corn futures fell 5 cents to $4.91-1/4 a bushel, while CBOT March wheat dropped 4 cents to $6.34-3/4 a bushel.
(Additional reporting by Gus Trompiz in Paris and Naveen Thukral in Singapore; Editing by Subhranshu Sahu, Shailesh Kuber and David Evans)
