(Updates with closing prices, adds new analyst quote)
CHICAGO, Sept 13 (Reuters) - Chicago Board of Trade soybean futures eased on Thursday, giving up early gains after U.S. President Donald Trump said the United States was under no pressure to make a trade deal with China, the biggest buyer of the oilseed.
Wheat futures, which fell for the seventh time in the last eight sessions, faced pressure from the U.S. Agriculture Department's bigger-than-expected estimate of the Russian crop.
Concerns that dry conditions in the Black Sea region would limit the size of harvest in key export countries had supported wheat prices for much of the summer. The latest harvest outlook further dimmed prospects for U.S. supplies on the export market.
Corn followed wheat lower, with additional pressure coming from USDA's forecast for record U.S. yields this fall. Expectations for a record U.S. soybean harvest added to the overall bearish tone.
"We are getting closer to harvest," said Bill Gentry, a broker at Risk Management Commodities. "Upward momentum is hard to maintain when you get the combines running. No matter how you slice it there is going to be more than enough (supply)."
CBOT November soybean futures closed down 6-3/4 cents at $8.33-1/4 a bushel.
Soybeans initially firmed on news confirmed by White House economic adviser Larry Kudlow that the Trump administration had invited Chinese officials to restart trade talks. Chinese Foreign Ministry spokesman Geng Shuang told reporters that China welcomed the invitation, and the two countries were discussing the details.
But Trump said on Twitter that a Wall Street Journal story on Wednesday about the invitation from Treasury Secretary Steven Mnuchin amid rising U.S. political pressure on Trump to ease up on trade fights "has it wrong."
CBOT December soft red winter wheat futures ended off 9-3/4 cents at $4.97 a bushel.
The U.S. Department of Agriculture, in its monthly supply and demand report, increased its forecast for the Russian wheat harvest to 71 million tonnes, up from a previous estimate of 68 million tonnes. Many traders have expected lower output due to a European drought that has stoked fears of export curbs.
"Higher Russian wheat output is a bit of a surprise given the dry weather they had during the growing period," said Phin Ziebell, an agribusiness economist with National Australia Bank.
CBOT December corn was 2 cents lower at $3.50-1/2 a bushel. (Additional reporting by Naveen Thukral in Singapore and Sybille de La Hamaide in Paris; Editing by Keith Weir and Dan Grebler)