* Corn steadies after dropping on improved U.S. crop rating

* CBOT corn had become technically oversold -analysts

* Ukraine reports Russian attack on grain storage facilities

CHICAGO, Aug 16 (Reuters) - Chicago Board of Trade corn futures rose on Wednesday as the market recovered slightly after improved U.S. crop conditions and concerns about China's economy pushed prices to their lowest level since December 2020.

Soybean futures also rebounded from a slide on Tuesday.

The gains reflected uncertainty about the size of upcoming U.S. harvests, though weekly corn and soybean crop ratings the government issued on Monday exceeded analysts' expectations.

Technical buying and another Russian attack on Ukrainian grain storage facilities helped drive prices higher, brokers said. Russia has made regular air strikes on Ukrainian ports and grain silos since mid-July, when it pulled out of the U.N.-backed deal for Ukraine to export grain.

"The ag markets are seeing a corrective bounce," Bryant Sanderson, broker for CHS Hedging, said in a note.

"The increasing Russian attacks on grain facilities are lending support, but the market seems to only give it limited weight."

The most-active corn contract finished up 6 cents at $4.81-1/2 a bushel after earlier hitting its lowest price since Dec. 31, 2020, at $4.73-1/2 a bushel.

Recent losses had left the market oversold, said Tomm Pfitzenmaier, analyst for Summit Commodity Brokerage. He added that heat expected in the U.S. could trim corn crop yields, but projections for hefty ending stocks reduce concerns about unfavorable weather.

"The large U.S. crop, combined with what turned out to be a record large Brazilian corn, means that there will be no shortage of exportable corn and minimizes the impact of the problems in Ukraine," Pfitzenmaier said.

Soybeans jumped 18-1/4 cents to $13.23-1/2 a bushel at the CBOT. Wheat ended down 3/4-cent at $5.97-3/4 a bushel, after dropping on Tuesday to its lowest level since June 1.

Tight U.S. soy supplies and export demand helped support soybean futures, analysts said. The U.S. on Thursday is slated to issue weekly export sales data. (Reporting by Tom Polansek in Chicago. Additional reporting by Gus Trompiz in Paris and Naveen Thukral in Singapore; Editing by Marguerita Choy and Chizu Nomiyama)