May said that the British government requested that Russia explain which of these two possibilities it was by the end of 13 March 2018. She also said: "The extra-judicial killing of terrorists and dissidents outside Russia were given legal sanction by the Russian Parliament in 2006. And of course Russia used radiological substances in its barbaric assault on Mr Litvinenko." She said that the UK government would "consider in detail the response from the Russian State" and in the event that there was no credible response, the government would "conclude that this action amounts to an unlawful use of force by the Russian State against the United Kingdom" and measures would follow. British media billed the statement as "Theresa May's ultimatum to Putin."