July 30 (Reuters) -Spot basis bids for corn shipped by barge to U.S. Gulf Coast terminals softened on Tuesday while soybean barge bids firmed, reversing Monday's trends, traders said.

* Cash sales of corn from the 2023 harvest increased in some areas, pressuring Gulf values, as prospects for a large 2024 crop this autumn prompted farmers and commercial grain handlers to clear space, one Illinois merchandiser said.

* The U.S. Department of Agriculture late on Monday rated 68% of the U.S. corn crop in good to excellent condition in a weekly progress report, up a percentage point from the previous week, while analysts on average had expected a decline.

* The USDA's soybean ratings fell to 67% good-to-excellent, down from 68% a week earlier, but still the highest rating for this time of year since 2020.

* Chicago Board of Trade corn, wheat and soybean futures fell on Tuesday, settling near their lowest levels since 2020 as strong crop ratings and benign weather forecasts reinforced expectations of big U.S. harvests. GRA/

* CIF Gulf corn barges loaded in July traded at 72 cents over CBOT September futures CU24 and were re-bid around 70 cents over futures, down 1 cent from Monday's last bid. August barges were bid about 70 cents over futures, down a penny from Monday.

* FOB offers for corn shipments loaded from the Gulf in August held steady at around 79 cents over futures.

* For soybeans, CIF Gulf barges loaded in August were bid around 70 cents over CBOT August SQ24 soybean futures, up 3 cents from Monday. A few July-loaded soybean barges were bid at 85 cents over August futures, also up 3 cents from Monday.

* FOB export premiums for Gulf soybean shipments loaded in August were steady at around 87 cents over CBOT August futures.

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