Dec 12 (Reuters) - Spot basis bids for corn shipped by barge to the U.S. Gulf Coast continued to weaken on Thursday, reflecting a replenished supply pipeline after farmers sold corn this week, traders said, but soybean barge bids firmed on exporter demand for the oilseed.

* Farmer sales of corn slowed on Thursday but merchandisers reported busy movement in the previous two days as Chicago Board of Trade March corn futures notched a two-month high above $4.50 a bushel.

* At the Gulf, CIF corn barges loaded in December were offered on Thursday at 69 cents over CBOT March futures, down a penny from Wednesday's offer. Bids were quoted at 67 cents over futures.

* FOB offers for corn shipped from the Gulf in January held steady at around 87 cents over CBOT March futures.

* Soybean barge bids improved after the U.S. Department of Agriculture confirmed private sales of 334,000 metric tons of U.S. soybeans to undisclosed destinations, the government's first daily sales announcement in a week.

* Some traders believe Chinese buyers have been booking U.S. soybeans to build up strategic reserves while buying cheaper Brazilian supplies for crushing.

* CIF soybean barges loaded in December traded at 89 cents over CBOT January futures and were also re-bid at 89 cents over futures, up 1 cent from Wednesday. January soy barges traded at 90 cents over futures.

* FOB export premiums for January soybean shipments were steady at around 109 cents over futures.

* Weekly export sales data from the USDA fell below trade expectations. The USDA reported corn sales in the week to Dec. 5 at 946,900 metric tons, below trade expectations for 1.1 million to 1.9 million tons.

* The USDA reported soybean sales in the week to Dec. 5 at 1.174 million tons, below trade expectations for 1.5 million to 2.2 million tons, and weekly U.S. wheat sales of 290,200 tons, at the low end of expectations.

* Meanwhile, optimal weather has bolstered expectations of large Brazilian harvests. National crop agency Conab raised its estimate of Brazil's 2024/25 soybean harvest to 166.21 million metric tons, up a shade from its November estimate of 166.14 million tons, and oilseed crushing group Abiove pegged the crop at 168.7 million tons, up from 167.7 million in November.

(Reporting by Julie Ingwersen; Editing by Cynthia Osterman)

((Julie.ingwersen@thomsonreuters.com; 1-313-484-5283; Reuters Messaging: julie.ingwersen.thomsonreuters.com@reuters.net))

((For displays of CIF basis, click on the codes in brackets:

U.S. CIF Gulf soybeans

U.S. CIF Gulf corn

U.S. CIF Gulf SRW wheat

U.S. CIF Gulf HRW wheat For displays of FOB basis, please click on the following codes in brackets:

U.S. FOB Gulf corn

U.S. FOB Gulf soybeans

U.S. FOB Gulf SRW wheat

U.S. FOB Gulf HRW wheat

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 U.S. export sales estimates U.S. grain export summary Brazil soybean export prices Brazil corn export prices Argentina grain prices Russia grain prices ))