MOSCOW, April 18 – Alexei Miller, the CEO of Gazprom, said Monday that Ukraine will not be able to cancel the 10-year natural gas supply agreement that Kiev believes to be “extremely unfavorable.”

The possibility of challenging and cancelling the agreement in international courts had been disclosed on Friday by first deputy prosecutor general Renat Kuzmin.

“For the first time in history of relations with Ukraine a long-term contract base has been created,” Miller said, according to the Interfax report from Moscow. “The actins of implementing the contract cannot be questioned.”