Trafigura, Vitol, Mercuria and Abu Dhabi National Oil Co. are in talks with U.S. officials over licenses covering about 50 blacklisted vessels, Bloomberg reported Friday, citing people familiar with the discussions. Treasury officials are weighing requests individually, and no decisions have been finalized.

The push follows months of shipping disruption related to the Iran war. Tankers have been diverted onto longer routes, insurance costs have risen and vessels have been tied up in inefficient transfers around the Strait of Hormuz. Valero estimated last month that shipping U.S. crude to Asia cost $30 to $35 per barrel, compared with about $5 a year earlier. Asian orders for U.S. crude for November delivery fell roughly 50% in October, potentially putting shipments at their lowest level in seven years.

Energy Secretary Chris Wright said last month that Washington was exploring arrangements under which investors could acquire and refurbish blacklisted tankers to carry legitimate oil cargoes. As of November 4, U.S. sanctions covered 1,568 ships, including 462 crude tankers, according to Treasury data compiled by Bloomberg.

The impact would depend on which vessels receive licenses. Returning idle tankers to service would add capacity; authorizing ships already carrying sanctioned oil would do less to ease the shortage. Many blacklisted vessels are old and need repairs, inspections and insurance before they can enter conventional commercial service. U.S. approval would not automatically lift restrictions imposed by the European Union or Britain.