CHICAGOCHICAGO (Reuters) - Chinese state-owned firms bought at least 500,000 tonnes of U.S. soybeans on Thursday for shipment primarily from Pacific Northwest grain export terminals from June to September, two traders with knowledge of the deals said.

The purchases were the first since U.S. Agriculture Secretary Sonny Perdue said on Twitter that China had committed to buying an additional 10 million tonnes of U.S. soybeans during trade talks on Feb. 22.

(Reporting by Karl Plume in Chicago; editing by Jonathan Oatis)