Moscow is so angry that it is threatening to unleash a trade
war with Ukraine and punish Lithuania for pandering to the “treacherous”
behavior of the former Soviet republics.

Russia finds it particularly offensive that Kyiv’s drift toward Europe is occurring under Ukrainian President Viktor Yanukovych,
whom Moscow initially hailed as pro-Russian. Moscow thought that after
it managed to sign an agreement to rent the Sevastopol naval base
for the Black Sea Fleet for the next 10 years, it would be just as easy
to bring Ukraine into the Customs Union.

Read more here.