An oil tanker that has transported Venezuelan fuel to Cuba since April last year finished loading this week a 150,000-barrel cargo of gasoline, a shipping schedule seen by Reuters shows, a possible sign that the OPEC country could be preparing to send supplies to the island under U.S. supervision.As of Thursday, it was not clear yet if the vessel had left Venezuela as it was last spotted by monitoring service TankerTrackers.com in Venezuelan waters on Monday. Reuters could not confirm the tanker's ultimate destination. Any tanker now leaving Venezuelan waters can only do so with U.S.