Oct 8 (Reuters) -Basis bids for soybeans shipped by barge to the U.S. Gulf Coast firmed on Tuesday, supported by exporter demand for high-quality supplies of the oilseed, traders said.

* Traders noted talk of quality problems with the early soybean harvest in the Mississippi River Delta region, a factor that appeared to be driving demand for soybeans graded as U.S. no. 1.

* Basis bids for corn barges softened, reflecting pressure from the expanding U.S. harvest that was replenishing supply pipelines while demand was somewhat flat.

* Some Midwest producers are wrapping up the soybean harvest this week and will shift to corn in the coming days, traders said. Nationally, the USDA reported the soybean harvest as 47% complete by Sunday and the corn harvest as 30% finished, both ahead of average.

* Barge freight costs eased slightly in some areas from unusually high levels, one source said. BG/US

* Traders are watching for potential demand from China, the world's biggest soybean importer, after the country's seven-day "Golden Week" holiday wrapped up on Monday.

* The U.S. Department of Agriculture confirmed private sales of 166,000 metric tons of U.S. soybeans to China.

* At the Gulf, CIF October soybean barges were bid at 76 cents over Chicago Board of Trade's November soybean SX24 futures, up 2 cents from Monday. Soy barges loaded during Oct. 1-5 traded at 80 cents over futures.

* FOB Gulf offers for November soybean shipments were around 113 cents over futures, unchanged from Monday. December shipments were offered at around 97 cents over January SF25 futures, up 2 cents from Monday.

* For corn, CIF barges loaded in October were bid at around 69 cents over CBOT December CZ24 futures, down 2 cents from Monday. December corn barges traded at 83 cents over futures.

* FOB Gulf offers for November corn shipments were around 114 cents over futures, up 4 cents from Monday. December shipments were offered around 112 cents over futures, steady with Monday.

Reporting by Julie Ingwersen; Editing by Alan Barona

For displays of CIF basis, click on the codes in brackets: U.S. CIF Gulf soybeans GRYM U.S. CIF Gulf corn GRYN U.S. CIF Gulf SRW wheat GRYO U.S. CIF Gulf HRW wheat GRYP
For displays of FOB basis, please click on the following codes in brackets: U.S. FOB Gulf corn GRZC U.S. FOB Gulf soybeans GRZD U.S. FOB Gulf SRW wheat GRZE U.S. FOB Gulf HRW wheat GRZF LINKS Corn prices page: cpurl://apps.cp./cms/?pageid=corn-cash-market
Wheat prices page: cpurl://apps.cp./cms/?pageid=wheat-cash-market
U.S. barge freight BG/US
U.S. export sales estimates USDA/EST
U.S. grain export summary GRA/U
Brazil soybean export prices SYBS
Brazil corn export prices SYBX
Argentina grain prices GRA/ARG
Russia grain prices GRA/RU