* CBOT corn futures trade above $7 a bushel
* China cancels pricey U.S. corn purchases - USDA
* Mexico, unknown buyers strike deals for U.S. corn
* Soybean, wheat futures also rise
CHICAGO, May 5 (Reuters) - Chicago Board of Trade corn futures set their highest price in more than eight-years on Wednesday as concerns over global supplies and strong demand fueled strong gains.
Wheat and soybeans also jumped on supply concerns.
In the corn market, the biggest gains were in the December contract, which represents the U.S. crop that will be harvested this autumn, as farmers are focused on planting.
The corn market is "on mission to capture more acres" by using high prices to entice farmers to increase plantings, said Rich Feltes, head of market insights for broker RJ O'Brien.
The most-active corn contract on the CBOT was up 9-1/4 cents at $7.06 a bushel as of 12:55 p.m. CDT (1755 GMT). It earlier reached $7.08, the highest level since March 2013.
December corn was up 18 cents to a contract high of $5.98-1/2.
CBOT wheat climbed 15-1/4 cents to $7.42 a bushel, and soybeans were up 3-3/4 cents at $15.42 a bushel.
The U.S. Department of Agriculture reported that China canceled purchases of 140,000 tonnes of U.S. corn for delivery in the 2020/2021 marketing year, following the recent surge in prices.
Yet, the USDA also reported that exporters sold 184,100 tonnes of U.S. corn to Mexico and a total of 147,320 tonnes to unknown buyers.
In Brazil, a rival corn producer and exporter, weather forecasts showed little sign of rain relief for Brazil's dry southern crop-growing areas, analysts said. The unfavorable conditions kept the focus on global supply issues, despite planting progress in the United States.
Brazil's second annual crop is seen as crucial to boosting short-term availability ahead of the U.S. harvest later in the year. (Reporting by Tom Polansek in Chicago, Sybille de la Hamaide in Paris and Naveen Thukral in Singapore; Editing by Rashmi Aich, Chizu Nomiyama and Barbara Lewis)
