On Thursday, Lavrov had a different estimation of what is behind the friction between Russian Federation and the US and Britain, citing what he called the "categorical reluctance of the United States and its Western allies to agree that the 500-year-long period of Western domination in world affairs is coming to an end".
The PM said it marked the "single biggest expulsion in 30 years".
But the deadline passed on Tuesday night with Russian Foreign Minister Lavrov saying there would be no official response until Britain had provided a sample of the toxin and pursued the investigation through the "proper channels" of the Organization for the Prohibition of Chemical Weapons (OPCW), of which both Russia and the British are signatories.
Earlier, The White House threw its weight behind the United Kingdom in the case of a nerve agent attack on a former spy and his daughter, saying it shares the British assessment that Russian Federation is responsible for the attack.
"May said there was "no alternative conclusion" other than that the Russian state was culpable" for the attack on Skripal and his daughter, who fell ill from exposure to a substance called Novichok in the city of Salisbury on March 4 and are now in hospital.
She announced a range of economic and diplomatic measures, including the suspension of high-level contacts with Russian Federation.
An invitation for Russian Foreign Minister Sergey Lavrov to visit Britain has been canceled, and British ministers and royals won't attend the soccer World Cup in Russia this summer.
She vowed to clamp down on Russians suspected of "hostile state activity", freezing assets for those in Britain and detaining those arriving at the border.
"The United States believes that Russian Federation is responsible for the attack on two people in the United Kingdom, using a military-grade nerve agent", US Ambassador Nikki Haley told the meeting held at Britain's request.
"There is no place for these people - or their money - in our country", she said.
Accusation of Putin role in poisoning is shocking
The change was painful, he said, for nations that "are in the habit of ruling the roost". The conversations earlier this week seem to have had an effect - particularly in the U.S.
"I will announce the measures that we are going to take in the coming days", he said.
NATO Secretary-General Jens Stoltenberg said Britain could count on NATO's solidarity, but that it had not invoked the alliance's mutual defence clause.
The intervention by the White House follows angry exchanges between British and Russian representatives at an emergency meeting of the United Nations security Council and the UK's decision to expel 23 Russian diplomats.
Nauert - who was elevated to acting undersecretary after the firing of Steve Goldstein, himself collateral damage of the Tillerson dismissal - went on to say, "This latest action by Russian Federation fits into a pattern of behavior 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".
"There does not seem to be any real appetite so far to investigate the ill-gotten gains of the Russian elite that have been laundered through London", said John Lough, an associate fellow in the Eurasia program at the Chatham House think-tank. "It is not clear to me that London's response will hit the Kremlin where it hurts".
President Vladimir Putin's spokesman Dmitry Peskov today reiterated Moscow's position that Britain's accusations were unfounded and that the poisoning of Skripal and his daughter had "all the signs of a provocation". It refused to comply with Britain's demand for an explanation, saying the United Kingdom must first provide samples of the poison collected by investigators.
Hours before Trump issued what amounted to a "you're fired" tweet directed at Rex Tillerson earlier this week, the secretary of state had publicly called out Russian Federation as the source of a nerve agent attack on an ex-spy in Britain.
"Russia had nothing to do with this incident", Nebenzia told the council and again demanded proof of a link to Russian Federation.
"It is hard to say what may be happening in neighboring countries", he was quoted as saying by the Interfax news agency. "Now, one member stands accused of using chemical weapons on the sovereign soil of another member".