First of all, the problem with Gazprom is the price of gas, which has been raised significantly by Gazprom in the last few weeks. Secondly, Gazprom has a contract with Ukraine for the supply of gas, and one of the key elements in this contract is that the gas that passes through Ukraine has to be exported.
One of the elements considered in Europe as a possible way of assisting Ukraine is the virtual reverse. Gazprom is rather unhappy about the possibility of the virtual reverse, which would solve part of the problems of the Ukrainian gas sector.