The Foreign Office expelled four Russian diplomats from London over the murder of Alexander Litvinenko. The stumbling block is the Moscow government's refusal to Andrei Lugovoi, the main suspect in the murder of former Russian security agent Alexander Litvinenko, who died in London in November from radioactive poisoning. This move can seriously harm Russian relations with Britain. Moscow last night called the British move "immoral" and "provocative" and said it will formally retaliate today over the combative new stance from Gordon Brown's government, which marks a significant change in approach from that of Tony Blair.

Officials in Moscow last night warned that the move would badly damage ties between the nations.

 Mikhail Kamynin, a foreign ministry spokesman, said: "They should understand well in London that the provocative actions conceived by the British authorities will not go unanswered and cannot fail to produce the most serious consequences for Russian-British relations as a whole."

Britain will also press for a European Union response to Russia's refusal to hand over Mr Lugovoi.

The Foreign Office refused to name the Russian officials being expelled. But it is believed that they will be some of the 30 or so Russian intelligence agents MI5 believes are active in the UK.

Russia has repeatedly refused to extradite Mr Lugovoi, saying the Russian constitution prevents it. Mr Miliband said that argument was open to legal challenge.

 Despite talk that Mr Lugovoi could stand trial either in a third country or in Russia under UK law, the minister was adamant that the only "appropriate venue for the trial is London". Russian lower Mr. Borshchevsky has supposed that if Russia cant extradite Mr. Lugovoi, he can leave for London on his free will. The Litvinenko case is just one of a number of simmering rows between Russia and the West.

At the weekend, Mr Putin also confirmed that Russia was pulling out of the Conventional Forces in Europe treaty, a post-Cold War agreement meant to curb military activity in eastern Europe.

Throwing out diplomats was once a staple of East-West relations, a common way for the two sides to swipe at each other within safe limits. But in the more finely nuanced era of post-Cold War foreign policy, expulsions are a diplomatic weapon of last resort, meant to signal extreme displeasure and the failure of negotiations.

For the previous years London has expelled 105 Russian diplomats, Moscow about 30.The last time Britain expelled Russians from the embassy in London was 1996, in retaliation for Moscow throwing out four UK diplomats it accused of spying for MI6.

But with Russia's oil and gas deposits being of increasing strategic and financial value, most western investors have been willing to endure tougher treatment from Moscow in the hope of commercial reward.

This has persuaded Mr Brown and Mr Miliband, the Foreign Secretary, that a stronger message was required over the Litvinenko case.

Sources:

    www.interfax.ru

    www.bloomberg.com