CHICAGO, March 7 (Reuters) - Chicago Board of Trade (CBOT) wheat futures rose on Thursday on bargain buying, rebounding after the most-active contract hit its lowest in more than three years, but the rally was capped by news that China cancelled a purchase of U.S. wheat and Egypt cancelled an international purchase tender, traders said.

Corn and soybean futures also rose, in part fuelled by short covering ahead of a monthly supply/demand report due Friday from the U.S. Department of Agriculture (USDA). Corn climbed about 2%, its biggest single-day rise since November, and soybeans rose as well. A weaker dollar made U.S. grains more competitive globally.

"Traders are covering their short positions because they can't push the price any lower," said Dan Norcini, an independent trader. "They have made a lot of money by selling short, and right now they're heading to the sidelines before the (USDA) report."

Wheat's rebound stalled after the USDA confirmed that exporters cancelled sales of 130,000 tons of U.S. soft red winter wheat to China. Also, Egypt, among the world's biggest wheat importers, cancelled an international wheat purchase tender.

CBOT May wheat slipped to a contract low before bouncing, although some analysts and traders thought the cancellations were already factored into the market.

As of 12:38 p.m. CST (1838 GMT), CBOT May wheat was up 1 cent at $5.32 per bushel, after falling to $5.28-1/2, a contract low and the lowest on a continuous chart of the most-active contract since August 2020.

CBOT May corn was up 9 cents at $4.37-3/4 a bushel and May soybeans were up 13-1/4 cents at $11.61-1/2 a bushel.

Corn and soybeans also struck multi-year lows in the past month, pressured by tepid Chinese demand and the prospect of large production South America despite mixed growing conditions.

Traders continue to square positions before Friday's USDA supply/demand report that will offer a gauge of South American corn and soybean production.

Meanwhile, soybean imports for top oilseed buyer China fell to a five-year low for the first two months of the year, weighed down by poor crushing margins and fewer ship arrivals during the Lunar New Year holidays, customs data showed. Imports for January and February combined were at 13.04 million metric tons, down 8.8% from the same period a year ago.

(Reporting by Heather Schlitz in Chicago; Additional reporting by Gus Trompiz in Paris and Naveen Thukral in Singapore; Editing by Richard Chang)