Shipments of refined products from French refinery and depots were blocked on Monday by a 13th day of strike action, though some refineries operated with a reduced flow.
The industrial action is part of a nationwide movement against pension system changes that lift the retirement age two years to 64. The changes were forced through parliament without a vote last week.
There is an increasing expectation of diesel supply shortages in France and Europe as a result of the strike-caused outages, which are weighing on North Sea and Nigerian crude prices and lifting the spot price of diesel higher than the forward price, traders said.
"We expect product shortages by April (in France)," one trader said. "The diesel market flipped from feeling long and heavy to short and very backward," another trader said.
There are no signs of increased export from the Middle East currently on the water to plug the supply gap, but there is expectation for more U.S. supplies as more Russian supplies go to Latin America.
Long-range tankers (LR2s) are unable to enter French ports currently due to the strike, restricting diesel imports, traders said.