(Updates with U.S. trading, adds analyst quote; changes byline, dateline, pvs SINGAPORE/PARIS)
CHICAGO, Sept 7 (Reuters) - U.S. corn futures on Thursday sagged 1.1 percent on technical selling and expectations of a U.S. bumper harvest that would enlarge the already massive global supply of the grain, traders said.
Wheat futures also fell, weighed down by weak worldwide demand for U.S. supplies.
Soybean futures were trading close to unchanged. Helping to underpin prices were concerns that Hurricane Irma will cut production in southern states such as Georgia and North Carolina.
"The beans are being supported by the hurricane," said Mark Gold, managing partner at Top Third Ag Marketing. "It is going to do some damage there."
At 10:55 a.m. CDT (1555 GMT), Chicago Board of Trade December corn futures were down 4 cents at $3.57 a bushel.
Corn futures firmed during overnight trading but hit resistance at their 20-day moving average, a level the December contract has not broken through since Aug. 10. Corn prices also tested that key technical point on Wednesday.
Traders also noted profit-taking following the corn market's run-up to a two-week high on Wednesday.
CBOT December wheat futures were down 9-1/4 cents at $4.36-1/2 a bushel.
Irma, which is expected to hit the U.S. mainland as early as this weekend, could also hamper exports, which would be another blow to the already light overseas interest in U.S. wheat stocks.
"Traders are also monitoring the Irma hurricane as its trajectory could hit the U.S. south-eastern coast, surely causing logistical issues," French consultancy Agritel said.
CBOT wheat had risen for four straight sessions and five of the previous six. Traders said that had caused some funds to back out of bullish bets built up during that run.
CBOT November soybeans were unchanged at $9.71 a bushel. (Additional reporting by Naveen Thukral in Singapore and Sybille de La Hamaide in Paris; Editing by Richard Pullin and David Goodman Editing by W Simon)