What is the reason for the ban on imports from the West?

Russia has announced a ban on imports of food and agricultural products from the United States, Europe and other Western countries.(29)The ban is for revenge on sanctions imposed by the West following Moscow’s forceful takeover of Crimea, and continued support for pro-Russian separatists in eastern Ukraine. The Russian measures will impact both sides.
    In a Cabinet meeting Thursday, Russian Prime Minister Dmitry Medvedev announced the embargo.
    "Russia is introducing a total ban on imports of beef, pork, fruit and vegetables, poultry, fish, cheese, milk and other dairy products from the European Union countries, the United States of America, Australia, Canada and the Kingdom of Norway," said Medvedev.(30)Russia imported about $1.3 billion of food and agricultural products from the U. S. in 2013. It bought close to $ 16 billion in products from Europe.