July 31 (Reuters) -Spot basis bids for corn shipped by barge to U.S. Gulf Coast terminals weakened on Wednesday, reflecting an uptick in farmer sales of old-crop grain as Chicago Board of Trade corn futures Cv1 fell to the lowest in nearly four years, traders said.

* Brokers reported scattered sales of both corn and soybeans as expectations for large U.S. crops this autumn prompted farmers and commercial grain handlers to clear space.

* At the CBOT, new-crop December corn futures CZ24 settled down 5-1/4 cents at $3.99-3/4 per bushel after dipping to $3.97-3/4, the lowest on a continuous chart of the most-active corn contract Cv1 since November 2020.

* CIF Gulf corn barges loaded in August were bid at about 68 cents over CBOT September CU24 corn futures, down 2 cants from Tuesday. September corn barges traded at 77 cents over September futures.

* FOB offers for corn shipments loaded from the Gulf in August were around 80 cents over futures.

* For soybeans, CIF Gulf barges loaded in August traded at 74 cents over CBOT August SQ24 soybean futures and were re-bid at 72 cents over futures, up 2 cents from Tuesday's last bid. Soybean barges loaded in November traded at 77 cents over CBOT November SX24 futures.

* FOB export premiums for Gulf soybean shipments loaded in September, the first month available, were around 115 cents over CBOT November SX24 futures, down 10 cents from Tuesday.

* The U.S. Department of Agriculture confirmed private sales of 104,572 metric tons of U.S. new-crop corn to undisclosed destinations.

* Ahead of Thursday's weekly USDA export sales report, traders expected the government to report U.S. sales of old-crop corn in the week ended July 25 at 275,000 to 600,000 metric tons and new-crop sales of 400,000 to 800,000 tons.

* Analysts estimated weekly old-crop soybean export sales at up to 300,000 tons and new-crop sales of up to 900,000 tons, while weekly new-crop wheat sales were seen at 250,000 to 550,000 tons.

Reporting by Julie Ingwersen; Editing by Sherry Jacob-Phillips

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