MOSCOW (Reuters) - Moscow finds that no progress has been made toward resolving a standoff with London over the poisoning of Russian former double agent Sergei Skripal and his daughter in Britain, Russia’s Foreign Minister Sergei Lavrov said on Wednesday.

Russia's Foreign Minister Sergei Lavrov speaks during a press conference with his Turkish counterpart Mevlut Cavusoglu in Moscow, Russia, March 14, 2018. REUTERS/Sergei Karpukhin

“There is only regress, we don’t see any progress,” Lavrov said, criticizing Britain for accusing Russia of involvement in the attack and describing such claims as neither robust nor serious.

Britain has said that it is “highly likely” Russia was behind the poisoning, which used a nerve agent developed by the Soviet military.

A stand-off between the two countries escalated on Wednesday after a midnight deadline set by British Prime Minister Theresa May expired without an explanation from the Kremlin about how the nerve agent could have appeared in Britain.

Lavrov said Russia would be ready to provide Britain with a response within 10 days if London submitted an official request, in line with the Chemical Weapons Convention.

“Instead of submitting such a request, Britain has continued to stage a political performance,” Lavrov said.

“Without concrete facts, it is a flagrant attempt to mislead the international community, to which we will have to respond,” the minister added.

Lavrov rejected British claims that no one other than Russia had a motive to target Skripal.

“Yesterday, both Russian and Western media platforms produced lots of arguments demonstrating that Russia did not have a motive, and that the only actors who could have had a motive to do this were those who want to continue a campaign of Russophobia,” Lavrov said.

Britain’s response to the expiry of the deadline and lack of explanation from Moscow was expected to be announced by May in parliament later, after she chaired a meeting of the National Security Council at her Downing Street office in the morning.