Leading senators called Tuesday on the United States to consider expelling up to 300 Russian diplomats unless Moscow issues more visas for the US embassy.
The United States protested when Moscow on August 1 barred embassies from hiring Russian or third-country staff, forcing Washington to lay off nearly 200 locals at missions across Russia.
In a letter to President Joe Biden, two Democratic and two Republican senators said that Russia has long counted local staff when calculating the number of US diplomats allowed.
As a result, some 400 Russian diplomats are now based in the United States and some 100 US diplomats are in Russia, they said.
"This disproportionality in diplomatic representation is unacceptable," wrote the senators who included Bob Menendez, chairman of the Senate Foreign Relations Committee, and Marco Rubio, a leading Republican.
"Russia must issue enough visas to approach parity between the number of American diplomats serving in Russia and the number of Russian diplomats serving in the United States. If such action is not taken, we urge you to begin expelling Russian diplomats, to bring the US diplomatic presence to parity."
The senators said that the dismissal of local staff has hindered the embassy's ability to handle Americans' consular needs as well as US policy interests.
The Biden administration in April expelled 10 Russian diplomats over what Washington alleged was Russian interference in the US election and a cyberattack.
Relations between the Cold War foes remain tense but have seen greater stability since Biden met Russian President Vladimir Putin in June in Geneva, tasking senior officials with further discussions on arms control and preventing miscalculations.