Early this week, an invoice was delivered to the Ukrainian government and Naftogaz, the country's national oil and natural gas company. It was sent by Russian energy giant Gazprom, and it read almost like a declaration of war: the Russians were demanding $7 billion for 16 billion cubic meters of natural gas -- which Ukraine hadn't even used. The principle at stake is "take or pay." According to a long-standing clause in Gazprom's supply agreement, customers are obligated to accept a contractually-agreed minimum quantity of natural gas, and even if the customer uses less, Moscow gets paid the full sum./.../Ukraine, a chronically cash-strapped key customer of the Russian company, is cutting down on gas imports. The "take or pay" contracts signed in 2009 foresaw annual deliveries of 41.6 billion cubic meters, but Kiev imported just 25.9 billion cubic meters in 2012. In 2013, it expects to import only 20 billion cubic meters.