CHICAGO, March 14 (Reuters) - Chicago Board of Trade (CBOT) wheat futures plunged on Thursday to approach their lowest level since 2020, and dragged corn prices down on spillover weakness, analysts said.

Soybeans bounced around on short-covering and profit-taking during a choppy session driven by technical trading.

Wheat's downward spiral was propelled by Chinese exporters' cancellation and postponement of around one million metric tons of Australian wheat and weak U.S. export sales released by the U.S. Department of Agriculture (USDA) on Thursday.

"As far as grains go, there's not lots of bullish news," Terry Reilly, senior agricultural specialist at Marex, said.

CBOT May wheat was down 11-1/2 cents at $5.32-3/4 a bushel at 1700 GMT, nearing Monday's low of $5.23-1/2 that was the lowest for a most-active contract since August 2020. May corn was down 7 cents at $4.34-1/4 a bushel.

May soybeans were up 1 cent at $11.97-3/4 a bushel after earlier surging above the $12 mark on technical buying.

Corn fell with wheat, despite export sales reaching the higher end of expectations and private sales of 100,000 tons of U.S. corn for delivery to Mexico reported by USDA on Thursday.

"Corn sales were good, but it wasn't anything out of line from where it should be," Karl Setzer, partner at Consus Ag Marketing, said. "Corn doesn't have support to move higher or lower. It's taking its direction from soy and wheat."

Soybeans spent much of the early session trading higher, but later eased as technical buying support faded.

Around 500,000 metric tons of U.S. wheat export sales to China have been cancelled in the last week, according to the USDA, likely due to the recent slide in prices. Traders are expecting further cancellations within the next week, analysts said.

At the same time, cheap Russian supply is creating stiff competition for remaining export demand. (Reporting by Heather Schlitz in Chicago. Additional reporting by Gus Trompiz in Paris and Peter Hobson in Canberra; Editing by Sherry Jacob-Phillips, Dhanya Ann Thoppil, Tasim Zahid and Barbara Lewis)