Wheat gains for 4th session, at near 3-week top on U.S. crop worries

* Wheat hits highest since Nov. 5 as U.S. winter crop deteriorates

* Dry weather in top producer Brazil supports soybeans

* Investors take positions ahead of long holiday weekend

SINGAPORE, Nov 25 (Reuters) - Chicago wheat futures rose for a fourth consecutive session on Wednesday to their highest since early November, as a crop quality downgrade by the U.S. government stoked concerns about global supplies.

Soybeans and corn rose in Asian trade.

"U.S. wheat prices are being driven up by the weekly crop condition report, which showed deterioration in winter crop condition," said one Singapore-based trader.

"The move in soybean prices depends on Chinese buying and as of now we see importers reducing purchases of U.S. beans for January shipment."

The most-active wheat contract on the Chicago Board Of Trade was up 0.2% at $6.18-1/2 a bushel by 0334 GMT, after climbing to its highest since Nov. 5 earlier in the session. Wheat closed up 2.2% on Tuesday.

Soybeans were up 0.4% to $11.95-1/2 a bushel and corn added 0.2% to $4.33-1/2 a bushel.

The United States Department of Agriculture (USDA) late on Monday rated 43% of the U.S. winter wheat crop in good to excellent condition, down from 46% a week earlier and bucking analyst expectations for a one-point improvement.

The biggest declines occurred in drought-hit states in the southern Plains.

Soybean prices were underpinned by dry weather across Brazil, the world's largest oilseed producer.

The USDA confirmed private sales of 334,000 tonnes of U.S. corn to unknown destinations, the latest in a series of daily corn sales announcements.

The wheat market drew additional support from positioning ahead of the holiday weekend.

The CBOT will be open for a shortened session on Friday after Thursday's holiday, but trade tends to be thin that day.

Commodity funds were net buyers of CBOT wheat and soymeal futures contracts on Tuesday and net sellers of corn, soyoil and soybean futures, traders said. (Reporting by Naveen Thukral; Editing by Ramakrishnan M.)