Russia’s once-dominant gas supply to Europe via Ukraine, which flowed for decades, is set to end on New Year’s Day with the collapse of a contract between the two warring countries that paid out billions to Moscow in gas revenue and to Kyiv in transit fees.

The future of gas transit through Ukraine is at a turning point. If a last-minute deal isn’t struck by Wednesday, billions of cubic meters in gas flows could come to a halt.

Russian gas flows through Ukraine are set to stop on Wednesday when a transit deal between the two countries expires in the wake of Moscow’s full-scale invasion. The pipeline was one of the last two routes still carrying Russian gas to Europe nearly three years into the full-scale war.