In late July, US President Donald Trump said Xi would visit Washington on September 24.

Farmer Lucas Richard of LFR Grain harvests a crop of soybeans at a farm in Hickory, North Carolina, United States, on Nov. 29. (Reuters/Charles Mostoller)

China has bought around 1 million metric tons of US soybeans this week, four traders told Reuters, as the world's top oilseed buyer steps up purchases ahead of Chinese President Xi Jinping's visit to Washington later this month.The purchases take China's total US soybean buying to nearly half of the 25 million tons the White House said Beijing had committed to annually through 2028.

While China's purchases of U.S. soybeans could help bolster trade and diplomatic ties with Washington, the buying also coincides with tightening global oilseed supplies amid dwindling inventories in top exporter Brazil.

"There have been more purchases made by Sinograin in the past few days," said one Asia-based trader. "They have been buying before Xi's visit to U.S."