The leaders of the United States, France and Germany joined Britain on Thursday in blaming Russia for poisoning a former spy with a powerful nerve agent, calling the attack 鈥渢he first offensive use of a nerve agent in Europe since the Second World War.鈥�

In a rare joint statement, U.S. President Donald Trump, French President Emmanuel Macron, German Chancellor Angela Merkel and British Prime Minister Theresa May said 鈥渢here is no plausible alternative explanation鈥� to Russian responsibility.

They said Russia鈥檚 failure to respond to Britain鈥檚 鈥渓egitimate request鈥� for an explanation 鈥渇urther underlines its responsibility.鈥�

The leaders said the use of a chemical weapon is 鈥渁n assault on U.K. sovereignty鈥� and 鈥渁 breach of international law.鈥�

The statement is the fruit of British efforts to enlist international support as it tries to hold Russia accountable for the March 4 attack that left former Russian double agent Sergei Skripal and his daughter Yulia in critical condition and a British police officer seriously ill.

U.K.-Russia relations have plunged to Cold War-era levels of iciness since the poisoning. May on Wednesday expelled 23 Russian diplomats, severed high-level contacts with Moscow and vowed both open and covert actions following the attack.

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Russia denies being the source of the nerve agent that poisoned the Skripals. Dmitry Peskov, the Kremlin spokesman, said Russia was 鈥渨orried by this situation鈥� and would work to express its position on the international stage.

Russian Foreign Minister Sergey Lavrov said Thursday that Moscow would 鈥渃ertainly鈥� expel some British diplomats in a tit-for-tat response.

Lavrov, in remarks carried by the RIA Novosti news agency, said the move would come 鈥渟oon,鈥� but added that Moscow would inform London through official channels before publicly announcing its countermeasures.

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

He argued that 鈥渂oorish and unfounded鈥� accusations against Russia 鈥渞eflect the hopeless situation the British government has found itself in when it can鈥檛 meet the obligations given to the public in connection with exit from the EU.鈥�

Kremlin spokesman Peskov said the decision about how to retaliate would come from President Vladimir Putin, 鈥渁nd there is no doubt that he will choose the option that best reflects Russian interests.鈥�

U.K. Defence Secretary Gavin Williamson called relations between the two countries 鈥渆xceptionally chilly鈥� and said Russia should 鈥済o away and shut up.鈥�

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

鈥淭he reason they鈥檝e chosen this nerve agent is to show that it鈥檚 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,鈥� Johnson told the BBC.

May announced the sanctions against Russia in 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 cancelled an invitation for Lavrov to visit. British ministers and royals also won鈥檛 attend the World Cup soccer tournament this summer in Russia, May said.

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

Britain is also trying to build a unified Western response, saying the attack in Salisbury is just the latest example of Russia鈥檚 disregard for international norms on the rule of law.

In their joint statement, Trump, Macron, Merkel and May cited 鈥渁 pattern of earlier irresponsible Russian behaviour鈥� and called on Russia to disclose details of its Novichok program to the Organization for the Prohibition of Chemical Weapons.

鈥淲e call on Russia to live up to its responsibilities as a member of the UN Security Council to uphold international peace and security,鈥� they said.

The leaders did not say what, if any, actions they would take if Russia does not comply.

May on Thursday went to the British city of Salisbury, to view the site where the Skripals were found critically ill.

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Angela Charlton in Moscow and Sylvie Corbet in Paris contributed

Danica Kirka, Jill Lawless And Vladimir Isachenkov, The Associated Press

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