This action is similar to that taken in November (before the EU accession discussion)...
Russia and Ukraine waged two gas wars over prices in the winters of 2006 and 2009 (which lasted 3 weeks) over a claim Ukraine was late in paying.
...
Ukrainian Prime Minister Mykola Azarov said that if Gazprom refuses to revise its contract, Ukraine would stop importing gas from Russia. In a step away from energy dependence on Russia, last week Ukraine signed a $10 billion shale gas deal with Chevron.
Ukraine is speeding up its effort to diversify its supply, and has looked at different exporters, fracking, new offshore projects in the Black Sea, as well as new LNG terminals and pipelines to diversify supply. Ukraine imports more than half of its gas from Russia, but under Viktor Yanukovich's leadership, has intentionally scaled down Gazprom imports 40 percent over 'unfair prices'.
Comment: Threat or promise? A US withdrawal is what Afghanistan has been hoping for since the start of the US war on Afghanistan in October 2001.