FACTBOX: Key strains in British-Russian relations

(Reuters) - Britain said on Monday it would expel four diplomats from the Russian embassy in London and suspend visa negotiations in retaliation for Moscow's refusal to extradite a suspect in the murder of Alexander Litvinenko.

Litvinenko, a former Russian state security officer turned critic of President Vladimir Putin, died an agonizing death in London from radioactive poisoning last year.

The row over suspect Andrei Lugovoy, a former state security agent, is the latest incident to strain Russo-British relations.

Following is a list of other major irritants:

* BORIS BEREZOVSKY

-- Moscow resents London's granting refugee status to an outspoken Kremlin critic, Russian tycoon Boris Berezovsky. Britain has repeatedly rejected Russian requests to extradite Berezovsky, wanted in Moscow on several criminal charges. Berezovsky, who lives in London since 2000, says the charges have been invented to silence him.

* AKHMED ZAKAYEV

-- Russia blames Britain for granting asylum to several leading Chechen rebels, most notably to Akhmed Zakayev. Russia says London's refusal to hand Zakayev over for trial betrays its double standards in dealing with the terrorist threat.

* OIL AND GAS

-- British oil major BP was forced last month to sell its stake in the Siberian Kovykta gas field to state-controlled firm Gazprom at a knock-down price.

-- The deal became part of the Kremlin drive to tighten its grip over Russia's oil and gas resources, fuelling concerns in the West about the safety of its own energy supplies.

-- Anglo-Dutch oil giant Royal Dutch Shell had to cede a part of its Sakhalin-2 project to Gazprom last December.

* KOSOVO

-- Russia has blocked a British draft resolution in the U.N. Security Council which would effectively give independence to Serbia's breakaway province of Kosovo. Moscow says it will not support any decision on Kosovo unless it is backed by Belgrade.

* DIPLOMACY

-- Last year activists from pro-Kremlin youth organization Nashi launched a months-long campaign against British ambassador Anthony Brenton, interrupting his speeches and banging their fists on his diplomatic Jaguar car.