The new Treasury sanctions escalated the tit-for-tat row between Russia and the West over Ukraine after Moscow threatened to cut off gas supplies to its neighbour unless it settled its unpaid bills -- a move that could wreak economic havoc on European countries that source gas from Ukraine.
Washington's latest sanctions hit back at that threat while also sending a warning to Kalashnikov-armed militants barricaded inside state buildings in two key cities in eastern Ukraine that following in Crimea's footsteps would have consequences.
The sanctions freeze the US-based assets of key Crimean breakaway leaders and gas company Chernomorneftegaz, whose funds were seized by the Crimean parliament and are now managed by Moscow.
The move came after embattled Ukrainian Prime Minister Arseniy Yatsenyuk vowed during a visit to the Donetsk coal mining zone to grant more power to the country's regions in a bid to soothe separatist tensions.
A similar occupation of the state security office of the hardscrabble eastern city of Lugansk has confronted Ukraine's untested leaders with their biggest challenge since their February ouster of Kremlin-backed president Viktor Yanukovych.
But Russian President Vladimir Putin -- his troops already massed along Ukraine's eastern border following their seizure of Crimea -- only upped the stakes by threatening to cut off Ukraine's gas over unpaid bills.
The decision could limit the supplies of at least 18 European nations for the third time since 2006. Each of the previous interruptions also coincided with attempts by Ukraine to pull itself out of the Kremlin's historic sphere of influence.
