A gas transportation agreement between Naftogaz Ukrayiny and Gazprom takes into account the right of the Ukrainian company to apply to arbitration in case of disputes, head of Naftogaz Ukrainy Yuriy Vitrenko said. "When Naftogaz exercises this right, it is a normal exercise of a contractual right, and not an 'unfriendly act.' Gazprom's threat to impose Russian sanctions against Naftogaz's legitimate use of this right once again proves the close relationship between Gazprom and the Russian state and jeopardizes the entire international mechanism for the peaceful settlement of disputes, to which Russia is a party in accordance with the New York Convention of 1958," he wrote on his Facebook page on Wednesday.