The widow of Russian spy Alexander Litvinenko has told ITV News she is "not fighting with Russia" in her battle to discover the circumstances surrounding his death.
Mr Litvinenko's family believes he was working for MI6 at the time of his death from radioactive poisoning and claim was killed on the orders of the Kremlin.
Speaking as a public inquiry into his death got underway, Marina Litvinenko said she "can't be calm until we realise who commited this crime".
The widow of a Russian spy poisoned in London has said the "whole world" will know the truth about what happened to her husband as a public inquiry into his death formally opened.
Marina Litvinenko said outside the Royal Courts of Justice she was positive the inquiry into her husband Alexander's death would get under way in January next year.
Sir Robert Owen, chair of the inquiry, praised the widow in the hearing for her patience in the face of "highly regrettable" delays.
Ms Litvinenko said today was a "special" day and she was confident the inquiry will start on schedule.
"Everybody all around the world will know the truth," she added.
A public inquiry into the death of spy Alexander Litvinenko - who was poisoned with radioactive polonium-210 - will be formally opened today.
The current inquest into the Russian spy's death will be suspended by coroner Sir Robert Owen before the inquiry is opened.
The 43-year-old fled to Britain in 2000 and was poisoned six years later while drinking tea with two Russian men, one a former KGB officer, at the Millennium Hotel in London's Grosvenor Square.
Mr Litvinenko's family believes he was working for MI6 at the time he was killed on the orders of the Kremlin.
Home Secretary Theresa May announced the inquiry last week after the Government had previously insisted it would "wait and see" what a judge-led inquest found.
Home Secretary Theresa May announced that a public inquiry will be held into the death of the former Russian spy Alexander Litvinenko today.Read the full story ›
The wife of Russian ex-spy Alexander Litvinenko has said she is "very pleased" over the decision to hold a public inquiry into his death.
Speaking to reporters, Marina Litvinenko said it still may take a "long time" to get the truth.
Mystery has surrounded the death of the KGB officer, after he died drinking tea laced with radioactive polonium-210 at a London hotel in 2006.
Earlier today, Home Secretary Theresa May announced the inquiry into his death in a written ministerial statement, saying: "I very much hope that this inquiry will be of some comfort to his widow."
Marina Litvinenko does not believe that Russian president Vladimir Putin will extradite the man named by prosecutors as the main suspect in the death of her husband.
Andrei Lugovoy, now a politician in Russia, was named by prosecutors as the main suspect in the case, but Marina Litvinenko said she thought it was unlikely that he would change his mind and extradite him.
Speaking to reporters she said: "I believe Putin will not change his decision to extradite or change his decision."
She added: "What I do is not against Russia because I am Russian and I love my country."
The widow of former Russian spy Alexander Litvinenko has said she fought for a public inquiry for "justice and truth."
Using the name her husband's loved ones knew him as, Marina Litvinenko told reporters: "For me it is very important because there is a lot of speculation about why Sacha died and what happened. I want to finish the speculation about his death."
She added: "It is very difficult to say what I feel exactly now but I was waiting for this day.... I'm for justice and truth."
There is "no link whatsoever" between the announcement of a public inquiry into the death of former spy Alexander Litvinenko and the current tensions with Russia over the Ukraine, according to David Cameron's official spokesman.
The probe will begin on July 31st and is planned to be complete by the end of next year, they said, adding that it will hold most of its hearings in public, although it could go into closed session if national security was put at risk.
Under the Inquiries Act, Sir Robert Owen who is leading the investigation will have the power to demand the production of witnesses and papers within UK jurisdiction, including agents and documents from the security and intelligence services.
However, he has no such powers in relation to evidence from Russia.
Alexander Litvinenko's widow said she is "relieved and delighted" that a public inquiry is to be held in her husband's 2006 death.
Referring to her husband as Sacha, the name her husband's loved ones knew him by, Marina Litvinenko said: "I am relieved and delighted with this decision. It sends a message to Sacha's murderers: no matter how strong and powerful you are, truth will win out in the end and you will be held accountable for your crimes.
She added: "It has taken nearly eight years to bring those culpable for Sacha's murder to justice. I look forward to the day when the truth behind my husband's murder is revealed for the whole world to see."
Last year, the government rejected a request for an inquiry into the killing of Litvinenko, who died after drinking tea poisoned with polonium - 210, a rare radioactive isotope.
In a letter to Sir Robert Owen, the current Coroner in the Inquest into Mr. Litvinenko’s death, May admitted "international relations" were a factor in the Government's decision.
Sir Robert will chair the new public inquiry.
Home Secretary Theresa May announced that a public inquiry will be held into the death of the former Russian spy Alexander Litvinenko.
May said: "I very much hope that this inquiry will be of some comfort to his widow."
Litvinenko, 43, died after drinking tea that was poisoned with the radioactive substance polonium-210.
His widow, Marina is expected to speak later today.