Feb 7 (Reuters) -Basis bids for soybeans and corn shipped by barge to the U.S. Gulf Coast declined on Tuesday, as barge freight costs fell, traders said.

* Bids for empty barges on the Illinois River for this week tumbled to 550% of tariff on Tuesday, from 625% a day earlier, barge sources said. Offers for spot barges fell about 25 percentage points on the Ohio River. BG/US

* Market players await the U.S. Department of Agriculture's monthly supply/demand report on Wednesday. Analysts surveyed by Reuters on average expect the government to lower its estimates of Argentina's corn and soy crops.

* CIF corn barges loaded in February were bid at 81 cents over Chicago Board of Trade (CBOT) March corn CH3 futures, down 5 cents from Monday's last bid. Corn barges loaded in March traded at both 86 cents and 85 cents over futures and were re-bid at 84 cents over futures.

* FOB basis offers for February corn shipments were steady at around 90 cents over CBOT March futures, and offers for March shipments held at 99 cents over futures.

* For soybeans, CIF barges loaded in February traded at 94 cents over CBOT March SH3 soybean futures, down 6 cents from Monday's trades, and were re-bid at 92 cents over futures, down 6 cents from Monday's last bid.

* FOB offers for February soybean shipments were around 118 cents over SH3 futures and March shipments were offered around 110 cents over futures, both down 2 cents from Monday.

Reporting by Julie Ingwersen

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