Marine fuel prices in Asia continue to climb amid tightening supplies and a robust rebound in oil, adding to the strain on crude shippers grappling with loss-making routes and facing lower near-term bookings.

Very low-sulfur fuel oil prices in Singapore have climbed almost 60% since the start of November to the highest level in a year, according to Intercontinental Exchange Inc. data. Supplies have tightened after refiners were forced to cut processing rates due to the Covid-19 pandemic and as a recent cold snap in northeast Asia led to a surge in demand for fuel oil in power generation.

The rally in Brent above $65 a barrel also means fuels produced from refining a barrel of crude are also climbing. This comes as tankers carrying oil on the key Saudi Arabia to China route are making a loss and as vessel demand is set to drop with some Asian refiners undertaking maintenance in March and April, meaning they will need less oil shipped to their operations.

Saudi Arabia’s pledge to deepen output cuts in February and March to support oil prices has removed a big slice of seaborne shipments from the market, while the number of available tankers to ship crude is expanding after the economics of storing oil at sea became less attractive. Most vessel owners will struggle to pass on higher fuel costs to charterers given the weak market, said Ralph Leszczynski, head of research at shipbroking firm Banchero Costa Group.

Shipowners may have to idle vessels temporarily and wait for the market to recover should the situation become more severe, said Jayendu Krishna, director at industry consultant Drewry Maritime Services Asia. Freight rates will remain under pressure during the first quarter, he said.

VLSFO supply in Asia, meanwhile, is expected to increase during the second quarter before tightening again in the second half of the year as refiners prioritize gasoline output, according to Daryl Tan, a consultant at FGE. This is due to general mobility rising as the vaccine is distributed more widely, which is set to coincide with summer driving demand in the U.S, he said.

Prompt VLSFO was at $479.93 a ton on Tuesday, the highest since February 2020, according to Intercontinental Exchange data. That’s up from about $305 at the start of November. High-sulfur fuel oil has also jumped over the same period, with 380-cst HSFO up almost 50% in Singapore. Still, the more sulfurous fuel is cheaper than VLSFO, meaning ships fitted with pollution reduction kits known as scrubbers are reaping some benefits from the price spread.