By Mark Weinraub

CHICAGO, Sept 14 (Reuters) - Chinese buyers booked their biggest deal for U.S. corn since Sept. 1, the U.S. Agriculture Department said on Monday, after focusing their attention on U.S. soybeans since the start of the month.

USDA said that private exporters reported the sale of 350,000 tonnes of corn to China for delivery in the 2020/21 marketing year, the biggest sale of corn to China since a deal for 596,000 tonnes on Sept. 1. The government also said that a corn sale of 140,000 tonnes announced on Aug. 27 that had been designated as headed to unknown destinations was corrected to destined for China.

China's agriculture ministry raised its forecasts for corn imports to 7 million tonnes for both the 2019/20 and 2020/21 crop years, keyed by large arrivals from the United States, according to a report published on its website on Saturday.

USDA data showed that China already has committed to buying around 9 million tonnes of corn from the United States for the 2020/21 marketing year, which would be a new record if it all gets shipped. During 2019/20, China imported 2.110 million tonnes of U.S. corn.

USDA also announced on Monday morning a sale of 129,000 tonnes of soybeans to China for delivery in 2020/21, the seventh straight trading day with an announcement of a soy sale to the world's top buyer of the oilseed.

China vowed to import $36.5 billion of U.S. agricultural goods annually as part of a Phase 1 trade deal signed in January. Chinese purchases through the first seven months of the year totaled just $8.559 billion, according to U.S. Census Bureau trade data.

At 9:20 a.m. CDT (1350 GMT) Chicago Board of Trade corn was up 1/2 cent at $3.69 after hitting a six-month high overnight.

(Reporting by Mark Weinraub in Chicago; editing by Jonathan Oatis)