The USDA, in its daily reporting system, said that private exporters indicated the deal was for the 2018/19 marketing year, which ends on Aug. 31.
China has stepped up its purchases of US soybeans during negotiations to end the trade war between the two countries but the amount purchased remained well below typical levels. The US soybean stockpile has ballooned to record levels during the dispute.
Trade talks are set to resume this week in Washington with a Chinese delegation led by Vice Premier Liu He. US President Donald Trump said on Friday that trade talks with China were going very well, but cautioned that he would not accept anything less than a "great deal."
China's State Council said on Sunday the country would continue to suspend additional tariffs on US vehicles and auto parts after April 1 in a goodwill gesture following a US decision to delay tariff hikes on Chinese imports.