Take context from the input text and decide on the accurate relationship between 'Naftogaz' and 'Ukraine' from the options provided.
Options: owned by, position held, parent organization, distribution format

"Since the additional agreement between Naftogaz and Gazprom is expiring on June 30, and the terms of further Russian gas deliveries to Ukraine were not agreed at today's trilateral talks in Vienna, Naftogaz is suspending purchases from the Russian company," the Ukrainian firm said in a statement.
owned by