The UK's attempts to extradite a man over Alexander Litvinenko's murder have not damaged relations with Russia, its first deputy prime minister has said.
Alexander Litvinenko died in hospital from radiation poisoning
Sergey Ivanov said the case was not connected with UK-Russia relations and there was "no problem".
He said Russian prosecutors would make "an independent decision" about an extradition request "based on the constitution and the Russian laws".
The UK wants to charge former KGB agent Andrei Lugovoi, who denies involvement.
Mr Litvinenko, 43, himself a former KGB officer, died in London on 23 November after exposure to the radioactive isotope polonium-210.
Mr Ivanov told a news conference: "There's no connection between the Litvinenko case and the UK/Russia relations.
"We have independent courts and prosecutors which, I hope, will receive official documents from the British side.
"They'll look at these papers and then make an independent decision which will be based on the constitution and the Russian laws.
"As for the UK/Russia relations, I think they're ok. No problem, as the British say."
Tony Blair has said the UK will not "shy away" from seeking justice.
His official spokesman said on Wednesday: "We believe Russia should abide by its international obligations, and we believe it's through abiding by international obligations that people can have confidence - whether it's in investment or international relations."
But the Kremlin maintains Russia's constitution does not allow it to hand over Mr Lugovoi.
Mr Litvinenko, who was a critic of Russian President Vladimir Putin, was granted political asylum in the UK in 2000 after defecting from Russia.
The UK's director of public prosecutions has recommended Mr Lugovoi be extradited to stand trial for the murder of Mr Litvinenko by "deliberate poisoning".
The formal submission of the UK's extradition request is expected to take place before the end of the week.
Andrei Lugovoi has strongly denied any involvement
In Moscow, the prosecutor-general's office said Russian citizens could not be extradited to a foreign country but could appear in a domestic court "with evidence provided by the foreign state".
Exiled Russian tycoon Boris Berezovsky, who the UK has refused to send back to Russia, said Mr Lugovoi would never be allowed to face trial in the UK.
The vocal critic of the Moscow regime also said he had no doubt President Putin had directly authorised the murder of Mr Litvinenko.
The Kremlin has previously dismissed such suggestions as "nonsense".
"It is impossible to produce polonium without state support and impossible to transport polonium... without state support," Mr Berezovsky said.
"It can't have happened without his personal involvement and that's exactly what Alexander told me in the hospital.
"Because of that, Lugovoi will never be extradited to London, and on the other hand I think Lugovoi's life is in danger, because it is absolutely the typical KGB way to solve the problem, to kill the witness of the crime."
On Tuesday Mr Lugovoi maintained the UK's request was "politically motivated" and described himself as a "victim not a perpetrator of a radiation attack" while in London.
Mr Lugovoi told Russian television: "I've said it before and I'll say it again - my family and myself were attacked when we were in the UK.
"I think today's charges are completely inadequate. I don't understand what proof they have or what motive they think I might have - or, indeed, how I could have done it.
"So I'm deeply surprised about the inadequate actions of the British law enforcement bodies."
Mr Lugovoi met Mr Litvinenko on the day he fell ill.
Polonium-210 was found in a string of places Mr Lugovoi visited in London, but he has insisted he is a witness not a suspect.
A documentary about the murder of Mr Litvinenko, called Rebellion: The Litvinenko Case, is to be screened at the Cannes film festival on Saturday.
The film, directed by Mr Litvinenko's friend Andrei Nekrasov, follows him in his last days and is highly critical of the Russian authorities.