"[Anyone] who fails to pay for the supplied goods should be aware that it is fraught with adverse consequences, including those related to the revocation of previously reached agreements on beneficial terms of supplies," the former Russian president said Tuesday.
In 2009, Russian energy company Gazprom cut gas supplies to Ukraine because of contractual disputes. That left European nations without a reliable source of natural gas as most of their supplies from Russia pass through the Soviet-era pipeline network in Ukraine.
Ukraine last year secured relief from its debt obligations by way of a discount for purchased volumes. Gazprom Chairman Alexei Miller said the discount will be suspended in April unless Ukraine settles its outstanding debt from 2013.
Miller said Ukraine paid "a little less than" half of its $1.3 billion in arrears.
U.S. Secretary of State John Kerry, who visited Kiev Tuesday, offered Ukraine $1 billion in loan guarantees.