Vlad is starting to sweat, his criminality is slowly starting to emerge so he is using threatening tactics, I presume.
The murder of Mr. Litvinenko put many hundreds of people's lives in jeopardy and he knows it, he knows there will be consequences if it is suggested beyond reasonable doubt that, that order came from the very top. He refused to extradite the two individuals and that, to me (being the cynical barsteward that I am) suggests he has something to hide.