Last year, China replaced the United States as the No. 1 importer of oil from Venezuela, yet another front in the heated rivalry between Washington and Beijing.

The United States had imposed sanctions on Venezuela's state-owned oil company as part of a bid to topple that country's socialist president, Nicolas Maduro. U.S. refineries stopped buying Venezuelan crude. Caracas' ally China, long a major customer, suddenly found itself as the top purchaser. Through the first six months of 2019, it imported an average of 350,000 barrels per day of crude from Venezuela.

But in August, Washington tightened its sanctions on Venezuela, warning that any foreign entity that continued to do business with the South American country's government could find itself subject to sanctions. State-owned China National Petroleum Corp, known as CNPC, stopped loading oil at Venezuelan ports that month. China's import data showed purchases started to slow, and by late 2019, abruptly stopped.