Kremlin promises retaliation against UK over diplomat expulsions after ex-spy's poisoning

Moscow continues to deny it poisoned a former spy living in England.

MOSCOW -- Russia is preparing retaliatory measures against the U.K. over its decision to expel 23 Russian diplomats, the Kremlin said today, promising they would "not be long in coming."

After Russian officials rejected an ultimatum from May to explain, she called the poisoning an “unlawful use of force.”

Russia has denied any involvement. Peskov, the Kremlin spokesman, today called the U.K.’s allegations “irresponsible” and suggested that the incident was meant as a “provocation” against Russia.

Russia’s foreign ministry today said it was drawing up a response to the U.K. measures. “There will be a response, I assure you,” Lavrov said at the forum, titled “Russia -- Land of Opportunity,” adding that Russia would inform the U.K. first before announcing it.

In previous diplomatic standoffs, Russia insisted it would follow a policy of “mirror” response, expelling the same number or proportion of diplomats. But Ministry spokeswoman Maria Zakharova suggested Wednesday night that Russia might consider different options.

“They will be appropriate, comparable -- I think here there is no need to get hung up on words -- mirror measures absolutely appropriate to the situation,” she said on Russia’s Channel 1.

He then alleged that the most likely scenario of the attack was a false-flag operation, perhaps done by the U.K. itself to “tarnish” Russia.

“The most probable source of this agent are the countries who have carried out research on these weapons, including Britain,” Nebenzia said.

“Let me make one thing clear from the very beginning: the United States stands in absolute solidarity with Great Britain,” Haley said. “The United States believes that Russia is responsible for the attack on two people in the United Kingdom using a military-grade nerve agent.”

The U.K.'s ambassador at the Security Council meeting pointed out that the U.K. has called on the OCPW to take part in the investigation.

The expulsion of the 23 diplomats, 40 percent of Russia’s embassy staff, according to the BBC, is the largest since 1971, when 100 Soviet diplomats and spies were ordered out.

But many Russians have viewed the expulsions as a surprisingly mild retaliation from the U.K.

“We are all in shock how soft the sanctions are,” Sergey Markov, a pro-government analyst who at one time advised the Kremlin, told ABC News. It was, he said, as though May had issued an ultimatum, obey or "we won't give you your tea."

Others have said the Kremlin will be more concerned by May’s comments that the U.K. may seek to take a more aggressive line against wealthy Russian figures allied with Putin. It was unclear from May's speech, however, that substantial actions targeting the assets of businessmen close to Putin were coming.

“I am not sure how committed the British government is to that idea,” said Fyodor Lukyanov, chairman of the Moscow-based Council of Foreign and Defense Policy, who sometimes advises Russia’s government.