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CHICAGO, Dec 7 (Reuters) - Chicago Board of Trade wheat futures slid to contract lows on Thursday, their fourth straight day of declines, on continued pressure from a Canadian report that showed harvest in that country was bigger than expected.
The decline in wheat weighed on corn prices. Soybeans also fell, pressured by a round of profit-taking after hitting their highest in more than three months on Tuesday, traders said.
Soybeans notched the biggest declines, shrugging off concerns about crop development in key suppliers Brazil and Argentina as well as bullish U.S. export data.
"Even with that (hot and dry) weather in South America. I still think it is a little early to suggest that we have problems there," said Mark Schultz, chief analyst at Minnesota-based Northstar Commodity Investment Co.
CBOT January soybean futures settled down 10-3/4 cents at $9.92 a bushel.
Soybeans also faced pressure from falling soymeal prices.
Selling in soybeans accelerated after prices fell through key technical support points.
CBOT March soft red winter wheat futures ended down 3-3/4 cents at $4.21-1/2 a bushel. Prices hit a contract low of $4.19-1/2 during the session. K.C. hard red winter wheat futures also hit new contract lows.
CBOT corn for March delivery dropped 1-1/4 cents to $3.51-1/2 a bushel.
The decline in wheat was unsurprising given slow U.S. exports, said Tobin Gorey, director of agricultural strategy at Commonwealth Bank of Australia.
"The catalyst seems to have been a higher estimate of Canada's wheat crop by the local official statistician," he said. "The estimate was the best part of 10 percent higher than where analysts were pegging the number, so it was a big shock."
Canadian farmers harvested larger crops than expected this autumn, reaping record-large canola output and a surprisingly big wheat crop, a Statistics Canada report showed on Wednesday.
The U.S. Agriculture Department on Thursday said weekly export sales of wheat totaled 323,000 tonnes. Analysts had been expecting wheat export sales in a range from 250,000 to 450,000 tonnes.
Soybean export sales came in at 2.086 million tonnes, topping forecasts that ranged from 1.000 million to 1.650 million tonnes.
Despite the recent strength in soybean prices, there was little upside potential for gains next year, Commerzbank said.
"The supply of soybeans will keep pace with the growing demand in China thanks to a record crop in the U.S. and only slightly lower crops in South America," it said in its outlook for 2018. (Additionl reporting by Naveen Thukral in Singapore and Sybille de La Hamaide in Paris; Editing by Marguerita Choy)