* Economic uncertainty hangs over grain markets
* Competition from Argentine soy adds pressure
* Traders eye favorable U.S. harvest weather
CHICAGO, Sept 16 (Reuters) - Chicago Board of Trade soybean futures stumbled on Friday as rising crop sales in Argentina and warnings of a recession raised concerns about global demand for U.S. supplies, analysts said.
Corn futures ended little changed, while wheat futures advanced.
Traders focused on demand for crops, after the U.S. Department of Agriculture updated its domestic production estimates in a monthly report issued on Monday.
"While we've answered a lot of the supply-side questions, now we have a ton of demand-side questions," said Ted Seifried, chief market strategist of Zaner Ag.
In Argentina, the world's top exporter of soy oil and meal and the No. 3 for raw beans, farmers increased sales of soybeans after the government implemented a more favorable exchange rate for exports of the cash crop. Until last month, local farmers were holding on to more soybeans than usual due to Argentina's uncertain economic environment.
"Competition from South American supplies continues to put pressure on U.S. soybean exports," analysts at Zhongzhou Futures in China said.
Most-active CBOT soybean futures closed 3 cents lower at $14.48-1/2 a bushel. Corn settled down 1/4 cent at $6.77-1/4 a bushel, while wheat jumped 14-3/4 cents to end at $8.59-3/4 a bushel.
Trading was choppy as investors weighed tighter U.S. crop inventories against uncertainty over demand.
"We're trying to juggle the idea of tighter-than-expected balance sheets, especially in soybeans," Seifried said. "We're kind of caught in between."
Next week, investors will wait for a U.S. Federal Reserve policy decision where the central bank is expected to deliver a hefty interest rate hike. Wall Street's major indexes closed lower on Friday as investors' fears about the prospects for a global recession intensified.
Traders will also monitor U.S. corn and soy harvests and crop development, which are generally benefiting from warm, dry weather. In the Southern Delta region, rain showers are not enough to hamper harvesting, Commodity Weather Group said.
(Reporting by Tom Polansek in Chicago, Gus Trompiz in Paris and Enrico Dela Cruz in Manila Editing by Diane Craft and Matthew Lewis)
