June 5 (Reuters) - Corn export premiums at the U.S. Gulf Coast rose on Tuesday in tandem with a firmer CIF barge basis as tight supplies of old-crop corn and lower futures prices supported values, traders said.
* Export interest for U.S. Gulf corn remained mostly slow as lower prices in South America undercut demand. Brazilian corn offered at $20 to $30 per tonne FOB discount to U.S.
* Brazil's government raised its corn crop estimate to a record 67.79 million tonnes after a huge jump in seeding of the winter crop, which will be harvested in coming weeks. Traders said exports could begin in late July.
* FOB corn basis offers at the Gulf rose to 85 cents a bushel over Chicago Board of Trade July futures, up about 5 cents from the previous day, traders said.
* CIF basis bids for first-half June corn barges at the Gulf were 80 over, up 4 cents on the day. Last-half June corn barges traded as high as 80 over and rebid at 81 over, up 5 cents from Monday, traders said.
* Argentine farmers called a one-week freeze on grain sales to protest agricultural policy. The strike caused some delays to grain loadings, traders said.
* Soybean export premiums at the Gulf mostly held steady, with poor near-term crush margins at Chinese processors limiting demand for spot shipments.
* Analysts Oil World said U.S. soybean exports in the first half of the 2012/13 marketing year would reach 33.5 million tonnes, up 39 percent from the prior year, due to lower South American supplies.
* Brazil's government trimmed its soy crop outlook due to drought, but the 66.37-million-tonne view remained above the USDA's 65 million.
* Wheat export premiums were quietly steady.
To check displays of FOB basis, click on following:
U.S. FOB Gulf corn
U.S. FOB Gulf soybeans
U.S. FOB Gulf SRW wheat
U.S. FOB Gulf HRW wheat
* FOB U.S. Gulf Grain
* U.S. grain export summary
* Brazil soybean export prices
* Brazil corn export prices
* Argentine grain prices
* Russian grain prices (Reporting by Karl Plume in Chicago; Editing by Dale Hudson)