WASHINGTON, Oct 5 (Reuters) - U.S. Democratic and Republican senators urged President Joe Biden on Tuesday to expel 300 Russian diplomats from the United States if Moscow does not issue more visas for Americans to represent Washington in Russia. The suggestion from the leaders of the Senate foreign relations and intelligence committees - Democrats Bob Menendez and Mark Warner and Republicans Jim Risch and Marco Rubio - would mark a sharp escalation in an ongoing dispute over embassy staffing amid tension between Washington and Moscow. Russia in August banned the U.S. embassy in Moscow from retaining, hiring or contracting Russian or third-country staff, except for guards, forcing the mission to let go 182 employees and dozens of contractors, the State Department said. read more That meant there are only about 100 U.S. diplomats in Russia, compared with 400 Russian diplomats across the United States, the senators said. "This disproportionality in diplomatic representation is unacceptable. Accordingly, 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," the senators wrote in a letter to Biden. If Moscow does not do so, they said Biden should begin expelling as many as 300 Russian diplomats. The White House and State Department did not immediately respond to a request for comment.