The widow of Alexander Litvinenko has appealed on Sky News for donations to help expose her husband's murderers.
Marina Litvinenko said she has to know the truth about the Russian dissident 's death in London from Polonium poisoning five years ago.
Mrs Litvinenko said she needs help because her legal costs for the upcoming inquest are likely to run to hundreds of thousands of pounds.
She told Sky News: "I have been approached by many people asking, 'Marina, how can we help you?' I appreciated it but said, 'I am okay,' I have the investigation here, my family and friends.
"Now, maybe, it is time to help me - even small donations will be very important."
Mr Litvinenko, 43, died of radioactive Polonium 210 poisoning in London's University College Hospital on November 23, 2006.
He had fallen ill shortly after drinking tea during a meeting with former KGB contacts at a West End hotel.
St Pancras coroner Dr Andrew Reid has indicated the inquest should be wide-ranging and is asking police and intelligence agencies MI5 and MI6 to carry out further inquiries.
Andrei Lugovoi , a former KGB agent, is wanted in London for the murder but Russia has dismissed calls for his extradition and instead gave him a seat in the Duma, its lower parliament.
Mrs Litvinenko said: "I appreciate everything that was done in the last five years but unfortunately nothing will change because every time Russia will refuse to extradite Lugovoi.
"I know I will be supported by the British government and they will ask to extradite Lugovoi but, until Lugovoi is present in a court in London, we will not know the truth."
She added: "It was an act of nuclear terrorism in London. That is why I strongly believe we have to know the truth."
Mrs Litvinenko said she had feared for her husband during his life but accepted he was passionately committed to speaking out.
"I loved Sasha how he was. He was an excellent man and honest person and what he did, he believed. I appreciated it and supported him (but) I knew it was very dangerous for him," she said.
Mr Litvinenko's death caused the biggest fallout from Britain and Russia since the Cold War.
On his deathbed, the dissident had accused then-president Vladimir Putin of ordering his murder - a claim the Kremlin denied.
Mr Lugovoi told Sky News last month that it looked "idiotic" that every British politician's first question when in Russia was about him.