* Wheat up on fresh Chinese demand

* Soybeans lower on favourable weather in Brazil

* Corn nearly unchanged

(New throughout, updates prices, market activity, adds US trading comments; changes dateline, previous PARIS/CANBERRA)

CHICAGO, Dec 5 (Reuters) - Chicago wheat futures rallied on Tuesday, extending a six-day ascent to highs not seen in more than three months, after the U.S. government announced another hefty private sale of U.S. wheat to China.

Soybeans declined, with the benchmark contract dropping below $13 a bushel on the prospect of rains in Brazil easing crop concerns, while corn was close to even in early-session trading.

The most-active wheat contract on the Chicago Board of Trade was up 7 cents or 1.1% at $6.27-1/2 a bushel as of 11:33 a.m. CST (1733 GMT), after rising to $6.36-1/4, the highest on a continuous chart since Aug. 25.

Wheat rose after U.S. Department of Agriculture (USDA) confirmed private sales of 198,000 metric tons of U.S. soft red winter wheat to China, the second such sale in as many days. Monday's announcement that China had purchased 440,000 tons of the grain, the largest one-off U.S. wheat export sale to China since at least 2020, added impetus to a recent rally.

"China typically doesn't import wheat from us. We typically don't sell wheat to anybody," said Ed Duggan, a risk management specialist at Top Third Ag Marketing.

The news buoyed a wheat market in which speculators and funds hold a huge net short position, making it vulnerable to bouts of short-covering that push prices higher.

CBOT corn was up 1-3/4 cents or 0.4% at $4.87-1/4 a bushel while the most-active soybean contract was down 10-1/2 cents or 0.8% at $12.95-3/4 a bushel, dropping to its lowest point since Oct. 26. Soybean traders continue to monitor weather conditions in drought-plagued Brazilian crop belts, where recent downpours coupled with a forecast of more rains in the coming weeks could bring much-needed relief to the region and bolster yield prospects in the world's biggest soy supplier.

Attention in grain markets is turning too towards Friday's monthly world crop report from the U.S. Department of Agriculture, which will include updated crop production estimates for South America. (Additional reporting by Gus Trompiz in Paris and Peter Hobson in Canberra; Editing by Emelia Sithole-Matarise)