The British Home Office has announced the launch of a public inquiry into the death of the former Russian spy Alexander Litvinenko, who died in London in 2006.
The ex-KGB officer died after drinking tea poisoned with radioactive polonium.
Litvinenko accused Russian President Vladimir Putin of ordering his murder.
The Kremlin denied involvement and refused to extradite suspect Andrei Lugovoi to the UK. Lugovoi has always denied the British charges.
Litvinenko’s widow Marina welcomed the new investigation, but told a news conference: “I believe Putin will not change his decision to extradite and he will not change [the] constitution.”
The announcement of the public inquiry came as British Prime Minister David Cameron pushed for tougher sanctions on Russia over the Ukraine crisis. A spokesperson for Cameron denied any link.