By Mark Weinraub

CHICAGO (Reuters) - China booked deals to buy 522,000 tonnes of soybeans, the U.S. Agriculture Department said on Thursday, the latest in a string of purchases by the world's top buyer of U.S. agricultural products.

Another 351,000 tonnes of soybeans were sold to buyers in unknown destinations, the USDA said. Traders and analysts said those soybeans also were likely headed to China.

In a separate report on Thursday, the USDA said that export sales of corn to China totaled 1.37 million tonnes in the week ended July 9, the biggest weekly total on record. China also bought 323,739 tonnes of wheat that week, its biggest weekly total since March. 

But weekly soybean export sales to China were just 383,216 tonnes, the smallest since the week ended April 16. 

There has been a flurry of farm commodity sales reported in recent days. Since Friday, the USDA has reported 3.259 million tonnes in U.S. corn purchases by China along with 1.04 million tonnes of soybeans and 320,000 tonnes of hard wheat. 

China said on Thursday it will stick to the Phase 1 trade deal it reached with the United States earlier this year but warned that it will respond to "bullying" tactics from Washington, as relations continue to deteriorate.

But China would need to dramatically ramp up buying of U.S. farm products in the coming months to fulfill its Phase 1 commitment to import $36.5 billion in the first year of the deal, signed in January.

U.S. government data shows that China imported just over $6 billion worth of U.S. farm goods from January to May.