Two China-flagged supertankers bound for Venezuela to pick up crude oil meant to service Caracas’ debt to Beijing have reversed course and are returning to Asia, shipping data shows, illustrating how U.S. restrictions continue to limit direct oil exports to China.

The very large crude carriers Xingye and Thousand Sunny — neither of which is under sanctions — had been positioned in the Atlantic Ocean awaiting orders amid ongoing disruption in Venezuela’s oil trade. Instead of loading cargoes, both vessels turned back, according to LSEG shipping data reviewed on Monday.

The U-turns come after the United States unveiled a deal last week to export up to 50 million barrels of Venezuelan oil held in storage. In announcing the agreement, U.S. President Donald Trump said China would still have access to Venezuelan crude, without specifying how that would occur while U.S. sanctions remain in effect.

While state-run PDVSA has not shipped any cargoes to China since last month, global traders including Vitol and Trafigura are preparing to move oil under the newly announced deal to destinations that could include the United States, India and China, potentially offering an indirect route for crude to reach China’s refiners.

The two supertankers were part of a small fleet that historically transported Venezuelan crude to China as debt payment. Before tighter U.S. sanctions on Venezuelan oil exports, China was the primary destination for Caracas’ crude, importing roughly three-quarters of the country’s total output.