China’s imports of copper concentrate from the United States hit their highest in June since September 2018, customs data showed on Sunday, as smelters made the most of a trade detente to purchase tariff-free metal earlier this year.

China, the world’s top copper consumer, imported 30,734 tonnes of U.S. copper concentrate last month, according to the General Administration of Customs. That accounted for 1.93% of its total June copper concentrate imports of 1.59 million tonnes.

The intensifying China-U.S. tensions had squeezed copper concentrate imports to China since late 2018, although Chinese firms had been allowed to apply for exemption on tariffs since March, with at least two cargoes of copper concentrate from the United States due to arrive in mid-June.

But tensions between the world’s two largest economies have escalated again, with each blaming the other for the covid-19 pandemic, and this week, China retaliating against a U.S. move to close the Chinese consulate in Houston.

It was not immediately clear who bought the concentrate that arrived in June, although the customs database showed cargoes had gone to Zhejiang and Fujian provinces.

Reuters reported in late May that two Chinese smelters had booked cargoes of U.S. copper concentrate after applying for exemptions on import duties under a scheme announced by the Ministry of Finance in February as part of trade war detente.

(By Pei Li, Min Zhang and Tom Daly; Editing by Sam Holmes)