WASHINGTON — A flurry of activity has been evident on the U.S. Department of Agriculture’s 24-hour reporting service so far this week, including both new export sales and cancellations of previously sold soybeans.

Today the U.S.D.A. said China, the largest importer of soybeans from the United States and the world, cancelled a previous purchase of 300,000 tonnes of soybeans for delivery in 2012-13, the current marketing year that began Sept. 1.

Also today there was a cancellation of 120,000 tonnes of soybeans sold to “unknown destinations” for delivery in 2012-13.

At the same time, “unknown destinations” bought 110,000 tonnes of soybeans for delivery during 2012-13 today, and on Monday bought 91,000 tonnes of soybeans for delivery in 2012-13 and 60,000 tonnes for delivery in 2013-14, according to the U.S.D.A.

“Unknown destinations” often is interpreted to be China, although that is not sure until destinations are revealed and/or changed closer to shipment.

Strong export sales of U.S. soybeans this fall have been supportive to U.S. soybean futures prices, although nearby months were down more than 20c a bu as of 8:30 a.m. Central Time this morning, in part on the latest export news.

Forecast record soybean production in South America in 2012-13, with harvest typically beginning later in the first quarter, and current favorable weather there, also weighed on futures prices this week and are expected to slow foreign demand for U.S. soybeans in coming months.