Russia today urged Britain not to politicise the row over its refusal to extradite the key suspect in Alexander Litvinenko's murder, saying it should be dealt with strictly as a legal case.
British officials have threatened unspecified steps against Russia for refusing to extradite Andrei Lugovoy, a former state security agent, to stand trial over the poisoning of Litvinenko in London last year.
One of the options available to London is to expel Russian diplomats - a possibility which revives memories of Cold War days and has alarmed officials there.
"If it is confirmed, as the British media report, that the British foreign ministry is dealing with it [Lugovoy's case] t becomes a political issue," Russian freign mister Sergei Lavrov told reporters.
"This case is a criminal one and should be dealt with by corresponding authorities ... we do not want to see it as political."
British prome minister Gordon Brown's official spokesman condemned Russia on Tuesday for refusing to extradite Lugovoy, saying its response was "extremely disappointing".
London's strong language has irritated Russian officials, who point out that their constitution prohibits the extradition of nationals.
A senior pro-Kremlin legislator said London's reaction was "entirely inappropriate".