Ukraine's free-trade agreement with the European Union came into force on January 1, coinciding with the start of Moscow's food embargo against Kyiv.
The free-trade deal, signed in June 2014, is part of the broader EU Association Agreement and stands at the heart of the drastic deterioration of Ukraine's relations with Russia.
The deal grants Ukraine tariff-free access to the EU's giant market and is expected to boost Ukraine's struggling economy.
The European Commission said in a statement of December 31 that "the agreement will contribute to the modernization and diversification of the Ukrainian economy and will create additional incentives for reform."
Ukraine, whose market has been traditionally oriented toward Russia, will now have to turn itself toward the European market and adapt to EU standards and rules.
Russia, furious at seeing its Soviet-era satellite turn to the West, has long been critical of the trade deal.
An initial attempt to finalize the pact had failed in 2013, sparking protests in Kyiv that led to the ouster of Ukraine's pro-Russian president, followed by Russia's annexation of Ukraine's Crimea, and a Russian-backed separatist uprising in eastern Ukraine.
Russia has taken retaliatory measures, suspending its free-trade agreement with Ukraine and banning the import of Ukrainian food.
Based on reporting by AFP and dpa