Marina Litvinenko is seeking to force Moscow to accept responsibility for her husband's death, as well as pay compensation,
The paper said Marina Litvinenko is expected to confirm that she is going ahead with her long-threatened legal action at a high-profile media event in London this week to mark the first anniversary of Alexander Litvinenko's death.
Marina Litvinenko's lawyers are likely to argue that the lethal polonium 210 used to poison her husband could have only been obtained by a state-sponsored group. They are expected to try and prove that that state was Russia.
Andrei Lugovoi, an ex-Kremlin bodyguard who London accuses of poisoning Alexander Litvinenko, said that by taking action against Russia, Marina Litvinenko was not seeking to establish the truth, but to cash in on a tragedy.
Russia's refusal to extradite Lugovoi to the U.K. has proved a major source of contention in relations between the countries, and in July sparked a tit-for-tat row involving expulsions of diplomats and visa restrictions.
In September, Lugovoi, a millionaire businessman who owns a private security company, confirmed that he would run for parliament as a candidate for the Liberal Democratic Party, led by outspoken pro-Kremlin ultranationalist Vladimir Zhirinovsky. Under Russian law, a seat in the State Duma would give Lugovoi immunity from prosecution.
