LONDON (AP) — Britain's prime minister chaired a meeting of the country's national security council Wednesday after Moscow ignored a midnight deadline to explain how a nerve agent developed by the Soviet Union was used against a former spy in England.
Theresa May is set to announce a range of economic and diplomatic measures against Russia in response to the assault on Sergei and Yulia Skripal. The father and daughter remain in critical condition in a hospital in Salisbury, southwestern England.
May said Monday that Russia is "highly likely" to blame, and that Moscow faced "extensive" retaliation if it could not explain how the nerve agent came to be used.
She is due to update lawmakers in the House of Commons Wednesday afternoon on what Britain will do to respond. The U.K. is likely to expel Russian diplomats, withdraw British officials from this summer's soccer World Cup in Russia and impose financial sanctions on Russians linked to President Vladimir Putin.
Moscow said it would not comply with Britain's demands unless the government provides samples of the poison collected by investigators.
Putin spokesman Dmitry Peskov told reporters on Wednesday that Russia "rejects the language of ultimatums."
Peskov said Britain has so far only offered "baseless accusations which are not backed up by any evidence." He said Russia would cooperate with the investigation but does not see Britain's willingness to reciprocate.
"We hope reason will prevail and other countries will think hard how serious the evidence against Russia is," he said.
Russia has claimed that the nerve agent could have come from another former Soviet country, pointing to Moscow's foe, Ukraine.
Lawmaker Vladimir Gutenev, a member of the state commission for chemical disarmament, said Russia had scrapped its stockpile of Novichok, the nerve agent used against the Skripals.
"It is hard to say what may be happening in neighboring countries," he was quoted as saying by the Interfax news agency.
Britain has sought support from allies in the European Union and NATO, including the United States. May's office says President Donald Trump told the prime minister the U.S. was "with the U.K. all the way."
On Wednesday it also called for an urgent meeting of the U.N. Security Council to discuss the investigation.
European Council President Donald Tusk said Wednesday that the attack was "most likely" inspired by Moscow and announced he would put the issue on the agenda at an EU leaders' summit next week.
Vladimir Isachenkov in Moscow and Raf Casert in Brussels contributed to this story.