* Soybeans, corn, wheat retreat from early highs
* USDA to issue grain stocks report on Fri
* Traders eye potential U.S. government shutdown
Sept 26 (Reuters) - Chicago soybean and corn futures on Tuesday retraced early gains as traders adjusted positions ahead of U.S. government data on grain and oilseed stockpiles due later this week, analysts said.
Worries about a possible U.S. government shutdown also hung over the markets.
Chicago Board of Trade (CBOT) November soybean futures climbed to $13.07-3/4 a bushel before dropping 3-3/4 cents to $12.94 a bushel by 11:15 a.m. CDT (1615 GMT).
Benchmark December corn crept down 3-3/4 cents to $4.77-1/2 a bushel after testing $4.83-1/2, its highest price in over a week. December wheat touched a one-week high of $5.96-3/4 a bushel before falling back toward its opening price of $5.89.
The U.S. Department of Agriculture is slated to issue a quarterly report on U.S. grain stockpiles at the end of the week.
"A lot of what we're seeing today is positioning ahead of Friday," said Karl Setzer, brokerage research lead for Bloomington, Illinois-based MidCo Commodities.
Setzer said the prospect of a U.S. government shutdown was another factor keeping prices in check.
"It's everything moving toward a point where there's just not a lot of interest," he said.
Wheat prices saw an early bounce after recent Russian attacks on Ukrainian ports created doubts about Kyiv's export capacity, while an unofficial minimum price for Russian wheat exports was also raising questions about Black Sea supply. Some of these concerns, though, have been offset by Russia's massive wheat harvest.
For soybeans, large supplies from Brazil have hampered demand for U.S. exports, while tight U.S. supplies have kept domestic prices elevated above the global market.
"While it seems hard to believe, even with the big losses we've had, we have to drive the market down even further to generate more demand," Setzer said. "The weak soy complex is pressuring corn, really in a sideways movement."
After markets closed on Monday, the USDA reported that soybean and corn harvests advanced more slowly last week than analysts had expected. (Reporting by Zachary Goelman in New York City; Additional reporting by Gus Trompiz in Paris and Naveen Thukral in Singapore; Editing by Richard Chang)
