A six-month halt to most Libyan oil production is degrading its quality and raising the likelihood of volumes never recovering to previous levels.
A permanent reduction in exports would be a blow for the Mediterranean tanker trade.
Five eastern terminals were shut down in January by forces loyal to rebel warlord Khalifa Haftar and his Libyan National Army (LNA).
State producer National Oil Corp (NOC) called this blockade "a historic crime against the people of Libya".
