The UN Secretary-General has said he is "very concerned"
The White House press secretary Sarah Sanders has said Russia's expulsion of US diplomats marks a "further deterioration" in relations between the two countries.
Ms Sanders suggested Washington may hit back, by saying: "Russia's response was not unanticipated, and the United States will deal with it."
Russia's move is seen as a retaliation to the expulsion of more than 150 Russian diplomats across the globe, following the poisoning of former Russian spy Sergei Skripal and his daughter Yulia in the UK.
Russian foreign minister Sergei Lavrov said US ambassador Jon Huntsman had been summoned and was informed of the "retaliatory measures".
Mr Lavrov promised "symmetrical measures" for other countries which are expelling Russian diplomats in a mass show of support for Britain.
Ireland announced earlier this week that one Russian diplomat is to leave the country.
The US has said there is "no justification" for Russia's move to expel diplomats and says the country should not act "like a victim".
Sergei Skirpal (66) and his daughter Yulia (33) were found unresponsive and taken to Salisbury District Hospital after being attacked with nerve agent novichok on March 4th.
Britain has blamed Moscow for the attempted murders - an allegation Russian President Vladimir Putin has dismissed as "nonsense".
On Thursday, it was announced that Ms Skripal was no longer in a critical condition and is "improving rapidly", but her father remains in a critical but stable condition.
Hitting out at the "so-called Skripal case", Mr Lavrov said Russia's measures were a reaction to "absolutely unacceptable actions that are taken against us under very harsh pressure from the United States and Britain".
He accused London of "forcing everyone to follow an anti-Russian course" and said Moscow had repeated its request for access to Ms Skripal "as she is a Russian citizen".
The foreign minister said in Moscow "we want to establish the truth" over the poisoning and accused Britain of "making mockery of international law".
Mr Lavrov added that Russia had asked for a meeting with the executive council of the Organisation for the Prohibition of Chemical Weapons on Tuesday to ask questions to "establish the truth".
"We are counting on our Western partners not evading an honest conversation," Mr Lavrov said.
UN Secretary-General Antonio Guterres has said he is "very concerned" that the world appeared to be approaching a situation "similar" to the Cold War as tensions rise between the US and Russia.