“This is possible but there are procedures we need to go through in Ukraine such as amending the constitution, which can be done either by the parliament or through a referendum,” Viktor Yanukovich told reporters after meeting Russian President Dmitry Medvedev.
He did not give further details.
Ukraine is in talks with the European Union on signing an association agreement which includes a free trade deal, but Brussels has not promised it EU membership or proposed that it be given EU-candidate status.
Joining the Russia-dominated trade bloc may hamper a deal with the EU because the customs union has a common foreign trade policy with tight links to Russia.
Russia pushed through the customs union after losing patience over its bid to join the World Trade Organization.
Russia, Belarus and Kazakhstan signed a macroeconomic policy coordination agreement last week, a key part of their drive to create a free trade zone in 2012.
SAince coming to power in February 2009, Yanukovich has tilted Ukraine’s foreign policy toward Russia, abandoned the goal of joining NATO and extended the deal under which the Russian navy uses Ukrainian Black Sea facilities.
He has, however, said Ukraine remained committed to European integration and urged the EU — Ukraine’s main trading partner — to recognize it as a potential member state.
