An oil tanker transporting Russian fuel to Cuba appears to have stalled roughly 1,000 miles (1,600 kilometers) off the coast, dealing a fresh blow as the island faces its worst fuel crisis in decades.

The ship, a sanctioned Russian tanker named Universal, has been drifting on the ocean since mid-April, when it halted the voyage that started in Russia, according to vessel movements tracked by Bloomberg. It’s carrying nearly 270,000 barrels of diesel for the island nation, data from maritime intelligence firm Vortexa Ltd. show.