The order to carry out the Salisbury nerve agent attack came from the "highest level" of the Russian state, Britain's Home Secretary says.
Sajid Javid stopped short of naming Russian President Vladimir Putin as the man who authorised the Novichok poisoning by the military intelligence service GRU but said "we all know what's at the top of the Russian government".
Although the suspects had been identified as GRU agents Alexander Petrov and Ruslan Boshirov and arrest warrants had been issued, "the reality is we will probably never see them in the UK" because they were unlikely to leave Russia again, Javid acknowledged.
Home Secretary Sajid Javid. Source: AAP
UK Prime Minister Theresa May has previously said the attack was "almost certainly" approved at a "senior level" of the Russian state, while Security Minister Ben Wallace said Putin bore ultimate responsibility as head of the government in Moscow.
Javid told the BBC the GRU operated on a "very short leash from the Kremlin" and was "getting its instructions directly from the highest levels of the Russian government".
He said of the "sickening and despicable" attack: "Unequivocally, crystal clear this was the act of the Russian state, two Russian nationals sent to Britain with the sole purpose of carrying out a reckless assassination attempt."
The home secretary said the UK had "considerable powers" to respond to Russia.
"We will bring all those powers, both overt and covert, to bear on Russia and what it represents today."
