March 15 (UPI) -- The United States, Britain, France and Germany jointly blamed the Russian government Thursday for the near-fatal poisoning of a former Russian spy and his daughter nearly two weeks ago.
In a statement, the four countries said "there is no plausible alternative explanation" to the attack -- which was supposedly the first offensive use of a nerve agent in Europe since World War II.
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 pair remain hospitalized in critical condition.
"This use of a military-grade nerve agent, of a type developed by Russia, constitutes the first offensive use of a nerve agent in Europe since the Second World War. It is an assault on the United Kingdom's sovereignty and any such use by a state party is a clear violation of the Chemical Weapons Convention and a breach of international law," the statement said. "It threatens the security of us all."
The statement follows a midnight deadline Wednesday for Russia to answer the accusations, imposed by British Prime Minister Theresa May. Moscow did not address the matter before the deadline.
"We share the United Kingdom's assessment that there is no plausible alternative explanation, and note that Russia´s failure to address the legitimate request by the government of the United Kingdom further underlines Russia's responsibility," the Western nations said in their statement.
The joint statement Thursday came a day after U.S. Ambassador to the United Nations Nikki Haley told the U.N. Security Council Wednesday that Moscow was behind the attack.
"The United States believes that Russia is responsible for the attack on two people in the United Kingdom using a military-grade nerve agent," Haley told the council.
The Trump administration diplomat said the United States "stands in absolute solidarity" with Britain, which moved Wednesday to expel 23 Russian diplomats.
Russia has denied responsibility for the poisoning, and Russian Foreign Minister Sergey Lavrov called the accusations a "Russophobic campaign." Thursday, Kremlin spokesman Dmitry Peskov said Russian President Vladimir Putin is mulling retaliatory measures against London.
"We consider the British position absolutely irresponsible with regard to diplomatic relations, as well as final goals and interests of a real investigation and search for the people who are behind this and from the point of view of violation of the international law by the British side, which is also obvious," Peskov said.
Investigators said they have determined the Skripals were poisoned with a Russian-made nerve agent.
Haley said the poison attack is "Russia's crime" and added the use of chemical weapons was "not an isolated incident" for Moscow.
"The Russians complained recently that we criticize them too much," she said. "We take no pleasure in having to constantly criticize Russia, but we need Russia to stop giving us so many reasons to do so."
"This is a defining moment," Haley continued. "The credibility of this Council will not survive if we fail to hold Russia accountable."
Haley's remarks echoed statements made by May, who said it was "highly likely" that Russia was responsible for the attack.
"This was not just an act of attempted murder in Salisbury -- nor just an act against U.K.," May said on Wednesday. "It is an affront to the prohibition on the use of chemical weapons."