The cost to ship crude oil on super-sized tankers from the U.S. Gulf Coast to the U.K. and Asia surged after attacks on vessels in the Black Sea unleashed a risk-based premium into global shipping markets. 

Tanker rates for so-called Very Large Crude Carriers that can carry about 2 million barrels of crude from the U.S. Gulf Coast to Asian markets jumped to about $7 million on Friday from $4.4 million just three days ago, according to two shipbrokers familiar with the trades. Rates for booking vessels that carry oil to European markets rose to more than $2.75 million from about $1.6 million, they said. 

The higher costs may threaten U.S. oil exports even as Brent crude’s premium to U.S. oil futures is the biggest its been since the early days of the pandemic. 

Ship owners were already avoiding offering their vessels to collect crude from Russia while at least three merchant ships have been reportedly hit since Russian forces began the attack on its neighbor this week. Insurers are either not offering to cover vessels sailing into the Black Sea, or they’re demanding huge premiums to do so.