Marina Litvinenko met the ambassador after Britain's Crown Prosecution Service said it would demand the extradition of Andrei Lugovoy, another former Russian agent, for the murder by deliberate radiation poisoning of Litvinenko, who suffered a slow death in a London hospital last year.
''It was not an easy meeting for him because I asked him his opinion about the extradition of Mr Lugovoy from Russia,'' she told British television.
''He did not answer me, because it's not his decision.'' Russian judicial sources have ruled out handing over Lugovoy.
Litvinenko's widow said she would continue to fight for justice for herself and her son. She said she did not believe responsibility for her husband's murder lay with one person.
''We don't know why my husband was killed, and who asked for this murder,'' she said. ''I believe it was not only one person.'' In a statement released earlier today, Marina Litvinenko thanked British police for their investigation.
''It is thanks to them that we have reached the point today of having a named person to be charged with this crime.
''I am now very anxious to see that justice is really done and that Mr Lugovoy is extradited and brought to trial in a UK court.'' REUTERS DS ND1942