Ukrainian President Viktor Yanukovych arrived Monday in Moscow to discuss energy policy with Kremlin officials. Dmitry Peskov, a spokesman for Russian President Vladimir Putin, told state news agency RIA Novosti that both sides were expected to discuss pricing issues.
Russian energy company Gazprom said Ukraine's energy company Naftogaz owes it $7 billion for unused natural gas covered under a take-or-pay scheme.
Former Ukrainian Prime Minister Yulia Tymoshenko is serving a seven-year prison sentence after being convicted on charges she overstepped her authority when she helped broker a deal with Gazprom in 2009. Kiev maintains it's paying too much for Russian natural gas when compared to other European countries.
Azarov said his government overpays Gazprom on a regular basis.
"We very politely replied that we do not consider the $7 billion claim to be justified and we will not pay it," he was quoted by the Interfax news agency as saying.