LONDON, July 19 (Reuters) - Britain said on Thursday that Russia's decision to throw out four of its diplomats was completely unjustified as the two countries squared up in a row over the death of emigre Alexander Litvinenko.

"We are disappointed that the Russian government should have signalled no new cooperation in the case of the extradition of Mr Andrei Lugovoy for the alleged murder of Alexander Litvinenko," British Foreign Secretary David Miliband said.

Britain said on Monday it was expelling four Russian diplomats over Moscow's refusal to extradite the main suspect in Litvinenko's murder.

"We obviously believe that the decision to expel four embassy staff was completely unjustified," he said, adding Britain was however heartened by expressions of support from the international community.