The war of words between Moscow and London over the poisoning of a former Russian spy on English soil escalated on Thursday, with a Russian lawmaker floating the bizarre theory that the United States provided the deadly nerve gas.

“The Americans had access not only to the technology, but had access to its development. In all likelihood, their NATO partners from Britain also had this access,” said Alexei Chepa, the deputy chair of the Russian parliament’s foreign-affairs committee.

The US participated in 1999 with Uzbekistan to clean up a site in the former Soviet republic where Novichok nerve gas was tested during the Cold War.

Russian Foreign Minister Sergey Lavrov said the Kremlin was weighing a response to Britain’s expulsion of 23 Russian envoys on Wednesday following the gassing of Sergei Skripal and his daughter Yulia.

Speaking of Russia’s role in the gassing, Boris Johnson, Lavrov’s British counterpart, said, “They want to simultaneously deny it, yet at the same time to glory in it.”

Russia’s ambassador to Britain, Alexander Yakovenko, said diplomats at their London embassy are getting death threats.

“There are quite a lot of mentally unbalanced people and people with a criminal past. You can expect anything from them , ” Yakovenko said.

With Post wires