"The British side has more than 50 more people", foreign ministry spokeswoman Maria Zakharova said.
British officials are considering granting a request by Russian Federation to visit Skripal's daughter, who is rapidly improving from the attack.
Also Saturday, Russian officials are questioning why British authorities searched a Moscow-bound plane Friday at London's Heathrow Airport.
The United States: Expelled 60 alleged spies posted around the country and at the Russian mission to the United Nations in what a senior USA official said was the biggest such move in US history. On Friday, Russia said it would limit the size of the British diplomatic mission to Russia to match that of Moscow's mission in Britain.
Bristow was summoned by Moscow along with the heads of missions from 23 other countries - majority European Union member states - who were told that some of their diplomats had to leave.
He is also said to have ordered aides not to talk publicly about tough measures he approves against Russian Federation because he doesn't want to anger Putin.
He said they included "the expulsion of the equivalent number of diplomats and our decision to withdraw permission for the functioning of the United States consulate general in Saint Petersburg".
Meanwhile, the British Foreign Office has said it is considering granting Russia's repeated requests for access to Yulia Skripal, daughter of former spy Sergei Skripal.
Winter Storm Warning Issued
There have not yet been any strong indications which way the late spring and early summer will go weather-wise, he said. The following counties are now in a Winter Storm Warning: Lancaster, Gage, Jefferson, Pawnee, Saline and Seward county.
Britain has called it "highly likely" that Russian Federation was responsible for the Skripal attack using the Soviet-designed Novichok nerve agent.
Germany's foreign minister on Sunday (Apr 1) said his country remained open to dialogue with Russian Federation and hoped eventually to "rebuild trust", even as tensions soar following a wave of tit-for-tat diplomatic expulsions over a poisoning row.
U.S. Ambassador Jon Huntsman Jr. was summoned Thursday night to the Foreign Ministry, where Deputy Foreign Minister Sergei Ryabkov informed him of Russia's response.
When asked if that meant London would now have to cut exactly 50 diplomatic and technical staff, she said: "A little over 50".
United Kingdom said it was considering Moscow's request for consular access to Yulia Skripal. Britain said the search was routine. "Our diplomats were developing cooperation between Russian Federation and the United States in different areas, among which are business, science, culture, space exploration and joint search for prisoners of war and missing in action", Antonov said.
They came after Britain expelled 23 Russian diplomats and suspended high-level contacts, among other measures.
USA diplomatic staff continued to move items out from their consulate building in St Petersburg on Saturday (March 31) after Moscow ordered its closure and the expulsion of 60 United States diplomats on Thursday (March 29). Mr Skripal remains in a coma and in a critical condition but last week doctors said that his daughter had shown signs of recovery and her life was no longer in danger.