(QHA) - Ukraine's state energy firm Naftogas and Russia's Gazprom have signed a formal amendment to a gas contract cutting the price of Russian gas by a third for the first quarter of 2014, Interfax news agency said on Thursday. In December, Russia agreed to slash the price of gas for Ukraine to $268.50 per 1,000 cubic metres after Kiev walked away from a free trade pact with the European Union. According to the agreement, the new price level must be confirmed every quarter, an arrangement that creates financial leverage for Moscow to prevent Kiev from seeking to revive ties with the EU.