Britain's Prime Minister Theresa May, centre, is briefed by members of the police as she views the area where former Russian double agent Sergei Skripal and his daughter were found critically ill, in Salisbury, England, Thursday, March 15, 2018.
Accusations have been growing against Moscow over the March 4 attack, in which former Russian spy Sergei Skripal and his 33-year-old daughter were targeted by a nerve agent in a British shopping district.
The incident, involving the first use of nerve agent in Europe since World War II, "threatens all of our security", the leaders, including Prime Minister Theresa May, said in the statement issued by the German government.
Johnson said Britain would send a sample of the nerve agent to the Organisation for the Prevention of Chemical Weapons for them to independently assess it.
She said they were "undeclared intelligence officials" and accused Russian Federation of responding to the attack, which is denies, with "disdain".
In a joint statement, the countries said that "the United Kingdom briefed thoroughly its allies that it was highly likely that Russian Federation was responsible for the attack".
Haley added US officials stood "in absolutely solidarity" with Britain after the country expelled 23 Russian diplomats on Wednesday, a move it announced in response to nerve agent attack.
The walking dead: Living Romanian man fails to overturn death cert
Mr Reliu wants to file another lawsuit but has no money, and suffers from diabetes, which he says makes everything more hard . Constantin Reliu's wife, having heard nothing from him for years, applied successfully for a death notice in 2016.
May on Thursday visited Salisbury, a normally sedate city where police investigators in chemical protection suits and the army have been collecting evidence of the poisoning.
The president's assessment, which occurred shortly after his administration announced new sanctions against Russian entities for interference in the 2016 election, comes after the administration initially hedged on blaming Russia for the attack. Russian Federation killed the joint investigative mechanism when it found [Bashar] Assad liable for chemical attacks.
In a joint statement, they demanded Moscow "address all questions" related to the attack against Skripal, which they said amounted to a "breach of global law". Although, according to the retired spy, many questions arise regarding the time and place of the attempted murder, as well as the weapon.
"This latest action by Russian Federation fits into a pattern of behaviour in which Russian Federation disregards the global rules-based order, undermines the sovereignty and security of countries worldwide, and attempts to subvert and discredit Western democratic institutions and processes", she said.
Moscow refused to meet the UK's deadline to co-operate, prompting Mrs May to announce the diplomats' expulsion and other measures meant to send a "clear message" to Russian Federation. It said the UK's decision to expel 23 of its diplomats was "unacceptable and unworthy of the British government". The pair remain hospitalized in critical condition.
"Of course we will", Russian Foreign Minister Sergei Lavrov told journalists when asked whether Moscow would respond in kind.