Two China-flagged supertankers that were sailing toward Venezuela to load debt-paying crude cargoes have made a sudden U-turn and are now heading back to Asia, according to shipping data from LSEG cited by Reuters.

The very large crude carriers Xingye and Thousand Sunny had been anchored in the Atlantic Ocean for several weeks, awaiting instructions amid ongoing uncertainty around Venezuela’s oil exports. The ships are part of a small fleet that traditionally transports Venezuelan crude to China under oil-for-debt arrangements.

Their reversal highlights the growing challenges confronting Venezuela’s oil trade, which has been disrupted by a U.S. oil embargo on Caracas and heightened political instability following the capture of Venezuelan President Nicolás Maduro in U.S. custody.

Under the export strategy, Venezuela had been sending crude to China as a form of payment for debt owed to Beijing. However, the combination of sanctions, a U.S. blockade and internal turmoil appears to have forced these tankers to abandon their planned voyage to Venezuelan ports and return toward Asian waters.