Energy companies reviewing Ukrainian shale natural gas reserves suspended operations because of conflict in the east of the country. Kiev said Thursday the border city of Novoazovsk fell to pro-Russian separatists.
Europe relies on Russia for about a quarter of its natural gas needs, though nearly all of that runs through the Soviet-era pipeline network in Ukraine.
Novak said Wednesday there was no threat to European energy security.
"I would like to stress that Russia's stance on this issue remains unchanged," he said. "We will make maximum efforts to fulfill our contract obligations to European importers regardless of current political situation in this or that transit nation."
Russian President Vladimir Putin said from Belarus there were few options for Ukraine itself because of pending debt issues tied up in an international court of arbitration. Russian energy company Gazprom says Ukraine owes it billions of dollars in unpaid debt.
Members of the European Union met with their Russian and Ukrainian counterparts in Minsk in an effort to find a political solution to the crisis. Trilateral energy talks are scheduled next week.