Brussels, July 19 (RIA Novosti) The European Union has expressed concern over Russia's refusal to cooperate with Britain in extraditing the key suspect in the murder case of a Russian spy.

'The EU expresses its disappointment at Russia's failure to cooperate constructively with UK authorities,' EU president holder Portugal said in a statement Wednesday.

Russia has refused to extradite Andrei Lugovoi, charged with the poisoning of former Russian spy Alexander Litvinenko, citing Russia's constitution that does not permit the extradition of Russian nationals.

The EU stressed the importance of 'urgent and constructive cooperation by the Russian Federation on this issue'.

Britain has decided to expel four Russian diplomats and suspended visa facilitation talks with Moscow after Russia's refusal.