Media caption " Our quarrel is with Putin's Kremlin", Boris Johnson says.
A British inquiry said Putin had probably approved the murder of Litvinenko, though Russian Federation denied any involvement. NATO Secretary General Jens Stoltenberg followed that up Friday by saying that the incident reflected a Russian "pattern of reckless behavior" that includes cyberattacks and election meddling.
On Monday, Theresa May told Parliament that Russian Federation is "highly likely" to blame for poisoning Mr Skripal and his daughter with a military-grade nerve agent.
Sergei Skripal and his daughter Yulia remain in a critical condition after the March 4 attack in the English city of Salisbury.
It was discovered that they had been exposed to a lethal, military-grade nerve agent called Novichok.
Russia will soon expel British diplomats in retaliation for Britain's decision to kick out 23 Russian envoys over a chemical attack on a former Russian double agent, Foreign Minister Sergei Lavrov said on Thursday.
Yulia Skripal flew to London from Russian Federation on March 3, according to counter-terrorism police.
Johnson said the evidence of Russian guilt was "overwhelming" because only Moscow had access to the poison used and a motive for harming Skripal.
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"There is something in the kind of smug, sarcastic response that we've heard from the Russians that to me betokens their fundamental guilt", he told the BBC.
A T-80 battle tank during a fire demonstration at the Patriot military park outside Moscow. CREDIT Anton Novoderezhkin Tass via Getty Images
The first leg will be held in London, with the team going to Moscow to face them in the second leg, as the merging worlds of sport and politics collide again. But nerve agents are entirely different.
It has been reported that it is at least five to eight and possibly 10 times as strong as VX.
An alert published by the Department of Homeland Security and Federal Bureau of Investigation said a "multi-stage intrusion campaign by Russian government cyber actors" had targeted the networks of small commercial facilities "where they staged malware, conducted spear phishing, and gained remote access into energy sector networks".
Some scientists say it's feasible that the nerve agent could be made stable enough to travel and that various compounds could have been added to Novichok to make it a clear, colorless liquid resembling water, perfume or alcohol.
He said the best way to deal with them is to "attack their soft spot - which is the money they have".
"I'm absolutely certain that Russian Federation has underestimated the resolve and unity of North Atlantic Treaty Organisation allies when we have implemented different kinds of sanctions over the last years", Mr Stoltenberg added. "The position of the British side seems absolutely irresponsible to us", Kremlin spokesman Dmitry Peskov.
He said: "Sooner or later, the British will have to show some proof to those "colleagues" who say they are with United Kingdom on this; sooner or later will have to stand up its accusations". It said Britain would not have to wait long for Russia's response. "But to all appearances, they had no real concerns: they went to lunch and they went to a pub".
In a letter to the Times, Salisbury NHS Trust emergency medical consultant Stephen Davies said only three people - the Skripals and Det Sgt Nick Bailey - had needed treatment. "They may be alive, maybe not, maybe nothing happened at all". "Nobody talked to the doctors".
Lithuanian Foreign Minister Linas Linkevicius told The Associated Press that the Salisbury attack is a direct challenge to Europe that will likely be discussed at an European Union ministers' meeting Monday in Brussels.