Chinese exports of rare earths, a group of 17 minerals at the center of a trade dispute with Washington, rose 23% in May from the previous month, according to customs data on Monday.

Chinese exports of rare earths—17 key minerals at the heart of trade tensions with Washington—rose 23% in May compared to the previous month, customs data showed Monday. May shipments totaled 5,865 tons—still below last year’s level—but the monthly surge lifted year-to-date exports by 2.

The United States and China will resume high-level trade talks in London on Monday to ease disputes over rare-earth minerals and advanced technology after