CHICAGO, June 25 (Reuters) - Spot basis bids for corn and soybeans shipped by barge to U.S. Gulf Coast terminals firmed on Thursday, reflecting exporter demand at a time when recent declines in Chicago Board of Trade corn futures have stalled farmer selling, traders said.

• Brokers noted rumors that Chinese buyers were seeking offers for U.S. Gulf soybeans for September-October shipment, but details were sketchy.

• CIF Gulf soybean barges loaded in June were bid at 80 cents over CBOT July SN26 futures, up 2 cents from Wednesday, and July soybean barges traded at 90 cents over futures.

• FOB export premiums for soybean vessels loaded at the Gulf in July were steady at about 110 cents over July futures but premiums for August loadings, at 108 cents over August SQ26 futures, were up 3 cents.

• For corn, CIF barges loaded in June were bid at 83 cents over CBOT July CN26 futures, up 2 cents from a day earlier. July corn barges traded at 89 cents over futures and were re-bid at the same level, up 2 cents from Wednesday's last bid.

• FOB export premiums for Gulf corn vessels loaded in July were flat at about 103 cents over futures, but premiums for September, October and November loadings were up 10 to 14 cents from earlier this week.

• The U.S. Department of Agriculture reported net export sales of U.S. old-crop corn in the week ended June 18 at 743,100 metric tons, down 27% from the prior four-week average, and new-crop corn sales totaled 735,900 tons.

• Net export sales of U.S. old-crop soybeans totaled 455,400 tons for the week while new-crop sales reached 902,200 tons, the USDA said, in line with trade expectations.

• Weekly net sales of U.S. wheat totaled 504,500 tons, in line with expectations.

• Market players were monitoring hot weather in Europe that could boost export demand for U.S. corn. Corn production in France could plunge by around 30% this year, the French agriculture ministry said.

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