CHICAGO, June 4 (Reuters) - Spot basis values for corn and soybeans shipped by barge to U.S. Gulf Coast export terminals ticked lower on Thursday, reflecting cooling demand from exporters following increased farmer grain offerings last month, traders said.

• Grain sales by producers have since stalled as Chicago Board of Trade corn CN26 and soybean SN26 futures have dropped sharply, pressured by improving U.S. crop production prospects and aggressive speculative selling. GRA/

• Some analysts attributed further CBOT declines on Thursday to new proposed U.S. tariffs on 60 countries, including China, that could threaten Chinese commitments to buy U.S. farm goods.

• CIF values continued to ease on Thursday as CBOT futures tumbled. At the Gulf, bids for CIF corn barges loaded in June were unquoted but offers were at 80 cents over CBOT July CN26 futures, down 2 cents from Wednesday.

• CIF July corn barges traded at 88 cents over futures for a second day, after trading at 89 cents over futures on Monday and Tuesday.

• FOB export premiums for Gulf corn vessels loaded in July held steady at around 102 cents over futures.

• For soybeans, CIF barges loaded in June were bid at 77 cents over CBOT July SN26 futures, down 3 cents from Wednesday.

• FOB export premiums for soybean vessels loaded at the Gulf in July were unchanged at around 108 cents over futures.

• The U.S. Department of Agriculture reported net export sales of U.S. old-crop corn in the week to May 28 at 883,300 metric tons, below trade expectations for 900,000 to 1,500,000 tons, while new-crop sales totaled 243,700 tons.

• Weekly net sales of old-crop soybeans totaled 276,900 tons, in line with expectations for 100,000 to 500,000 tons.

• For wheat, the USDA reported net sales reductions of 642,200 tons of old-crop wheat, and net sales of 838,500 tons of new-crop wheat.

• Under its daily reporting rules, the USDA confirmed private sales of 115,000 metric tons of U.S. new-crop corn to Colombia.

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