GRAINS-Corn, soy firm after benign USDA data as market looks ahead to U.S.-China trade deal

* USDA raises U.S. corn, soy production outlook

* USDA demand outlook in question ahead of U.S.-China trade deal

* Wheat turns down as U.S. winter crop acres near expectations (Adds USDA crop projections, updates prices, adds weekly trends)

CHICAGO, Jan 10 (Reuters) - U.S. corn and soybeans were steady to higher on Friday as investors looked past revised U.S. Department of Agriculture (USDA) supply-and-demand projections and focused on improved prospects for exports to China, which is due to sign an interim trade deal with the United States next week.

The USDA data, released during Friday’s trading session, showed modest changes to crop production and stocks but did not include the agency’s outlook for post-trade deal demand from China.

The USDA’s eagerly awaited estimates for 2019 U.S. corn and soybean production also remained uncertain after the agency said it would resurvey farmers in five northern states where poor weather left many acres unharvested.

“This report is not a game changer,” said Don Roose, president of U.S. Commodities in West Des Moines, Iowa.

“We were handcuffed going into the report with larger supplies around the world with improved weather in South America and hopes of some better demand from China. We come out of the report looking at the same thing,” he said.

The USDA unexpectedly raised its corn and soybean yield estimates, which surprised some traders following unfavorable crop weather last year followed by a challenging harvest. The increases were partly offset by fewer harvested acres.

U.S. corn production for the 2019/20 marketing year was 13.692 billion bushels, based on an average yield of 168.0 bushels per acre. Soybean production was 3.558 billion bushels, with average yields of 47.4 bushels per acre.

The government’s closely watched quarterly grain stocks data showed supplies down from a year ago.

South American crop forecasts were left unchanged.

U.S. winter wheat plantings declined, as expected, to the lowest point since 1909, although the USDA’s estimate was slightly above the average trade forecast.

Chicago Board of Trade March corn was 1 cent higher at $3.84-1/4 a bushel by 12:28 p.m. CST (1828 GMT), reversing a pre-report drop to $3.76-1/2 a bushel, the lowest since Dec. 13. The contract was on pace for a second straight weekly decline.

March soybeans gained 1-1/4 cents to $9.44-3/4. They had dropped shortly after the USDA data release to a three-week low of $9.35-1/2, but remained on pace for a small weekly gain.

CBOT March wheat fell 1/2 cent to $5.61-3/4 a bushel, but remained on track for a weekly advance of more than 1%. The contract peaked at $5.68-1/2 a bushel ahead of the report, which was the highest for a most-active contract since August 2018. (Reporting by Karl Plume in Chicago; Additional reporting by Nigel Hunt in London and Naveen Thukral in Singapore, Editing by Grant McCool and Tom Brown)