Russia will "certainly" expel British diplomats in a tit-for-tat response to Britain's decision to send 23 Russians home over the poisoning of a former spy, Russia's foreign minister said Thursday.

Sergey Lavrov, speaking in remarks carried by the RIA Novosti news agency, said the move would come "soon," but added that Moscow would inform London through official channels before publicly announcing its countermeasures.

British and Russian officials traded barbs as diplomatic relations plunged to Cold War-era levels of iciness following the nerve-agent poisoning of former spy Sergei Skripal and his daughter Yulia. Britain blames Russia for the March 4 attack, which has left the pair in critical condition and a police officer seriously ill.

U.K. Defense Secretary Gavin Williamson called relations between the two countries "exceptionally chilly" and said Russia should "go away and shut up."

Lavrov said British accusations of Moscow's involvement are intended to distract public attention from the U.K's troubled exit from the European Union.

He argued that "boorish and unfounded" accusations against Russia "reflect the hopeless situation the British government has found itself in when it can't meet the obligations given to the public in connection with exit from the EU."

British Foreign Secretary Boris Johnson said Russia targeted Skripal — a former Russian intelligence officer convicted of spying for Britain — to make it clear that those who defy the Russian state deserve to "choke on their own 30 pieces of silver."

Johnson told the BBC there was a message in the "smug, sarcastic response" from Moscow after Britain demanded an explanation for how a nerve agent developed by the Soviet Union's Novichok program was used on the Skripals in the English city of Salisbury. Johnson said the Russian government wants "simultaneously to deny it and yet at the same time to glory in it."

"The reason they've chosen this nerve agent is to show that it's Russia, and to show people in their agencies who might think of defecting or of supporting another way of life, of believing in an alternative set of values, that Russia will take revenge," Johnson said.

British Prime Minister Theresa May on Wednesday expelled 23 Russian diplomats, severed high-level contacts and vowed both open and covert action following the attack.

Kremlin spokesman Dmitry Peskov wouldn't reveal how Russia will retaliate, but said the decision will come from President Vladimir Putin, "and there is no doubt that he will choose the option that best reflects Russian interests."

"We are worried by this situation" and will work patiently to express Russia's position on the international stage, Peskov said.

May announced the sanctions against Russia in a speech to the House of Commons after Moscow ignored a deadline to explain its links to the attack on the Skripals.

As a result of the suspension of high-level contacts with Russia, Britain canceled an invitation for Lavrov to visit. British ministers and royals also won't attend the World Cup soccer tournament this summer in Russia, May said.

May also said Britain would clamp down on murky Russian money and strengthen the government's ability to impose sanctions on those who abuse human rights, though she gave few details.

Britain is also trying to build international consensus for a unified Western response, saying the attack in Salisbury is just the latest example of Russia's disregard for international norms on the rule of law. U.S. President Donald Trump and French President Emmanuel Macron are among the world leaders who have expressed solidarity with Britain.

Macron said Thursday that "everything seems to indicate Russia's responsibility," and France would take measures in coming days in response to the poisoning.