What is the relationship between Naftogaz and Ukraine in the context of the input sentence. Choose an answer from: product/material produced; manufacturer; distributed by; industry; position held; original broadcaster; owned by; founded by; distribution format; headquarters location; stock exchange; currency; parent organization; chief executive officer; director/manager; owner of; operator; member of; employer; chairperson; platform; subsidiary; legal form; publisher; developer; brand; business division; location of formation; creator.

"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.

Answer: owned_by