NATO has joined more than two dozen countries in expelling Russian representatives in an unprecedented show of support for Britain over the Salisbury nerve agent attack.
General-secretary Jens Stoltenberg said the permanent size of the Russian mission would be cut from 30 to 20 people.
"It sends a very clear message to Russia that it (Russian aggression) has costs and I actually think that Russia has underestimated the unity of NATO allies."
A total of 27 nations have now announced the expulsion of more than 140 Russian diplomats.
Moldova, Ireland, Australia and Belgium are the latest countries to act, after the UK made the first move by expelling 23 envoys earlier this month.
Meanwhile the White House has stressed that while it is open to building a better relationship with Russia, Moscow must understand there are serious consequences to its destabilizing actions.
Russia has denied involvement in the poisoning of double agent and his daughter and is said to be drawing up a number of possible retaliatory measures.