* Corn futures gain as traders cover short positions

* Soybeans follow energy prices lower; CBOT wheat flat

Sept 28 (Reuters) -

Chicago corn prices neared a three-week high on Thursday as speculators covered short positions while falling energy prices undercut a rally in oilseeds, traders and analysts said.

The markets are waiting for the U.S. Department of Agriculture to issue quarterly grain stocks data on Friday.

The most-active corn contract on the Chicago Board of Trade (CBOT) was up about 0.7% at $4.86-1/2 a bushel by 12:30 p.m. CDT (1730 GMT) and touched its highest price since Sept. 8.

"Why has the market been trying to grind higher the last number of days? I just think it's short-covering," said Tom Fritz, a partner with brokerage EFG Group in Chicago.

Fritz pointed to data from the Commodity Futures Trading Commission that last week showed speculative investors held a massive

net short position in corn

. He said they were likely being lured into buying back previously sold futures as corn hovered near three-year lows.

Fritz added that some of the short-covering was likely being fueled by traders repositioning ahead of the

release

on Friday of the USDA's closely watched stocks report.

CBOT soybean prices were down 0.2% to $13.00 a bushel after four straight sessions of gains. As crude oil

fell on Thursday

, soybeans, lead by soybean oil, followed.

"Soybeans are not finding the support from the energy that they found yesterday through that bean oil market," said Mike Zuzolo of Global Commodity Analytics in Atchison, Kansas.

December soybean oil was down about 1.9% at 57.15 cents per lb.

CBOT wheat traded sideways at around $5.80-1/4 a bushel in a choppy session, finding some strength from data showing better-than-expected weekly U.S.

export

sales.

Kansas City hard red winter wheat continued to drop after hitting two-year lows a day earlier, falling 7-1/4 cents to $6.87-1/4 a bushel. The spread between CBOT and Kansas City wheat fell to its narrowest since early March. (Reporting Zachary Goelman in New York City; Editing by Paul Simao)