"The compounds should be returned, and the sooner, the better. There should be no 'games,' 'bargaining,' 'exchanges,' preliminary conditions on this matter. It would be better if colleagues in the United States understood this before it becomes an irreversible problem of the Russian-US relations," Kosachev wrote on his official Facebook account.
The official said the senators' letter to Trump was a "scandal."
"The representatives of the supreme legislative body of the country, which is proud of its commitment to upholding the law, are openly calling on the head of the state to commit a direct and gross violation of international norms," Kosachev stressed.
The senators wrote their letter ahead of Trump's first ever meeting with Russian President Vladimir Putin expected to take place later in the day on the sidelines of the G20 Summit in Hamburg.
In December 2016, former US President Barack Obama’s administration approved a sanctions package against Russia due to its alleged meddling into the 2016 US elections. The measures included barring of access to two diplomatic compounds in use by the Russian Embassy in Washington and Russia’s Permanent Mission to the United Nations in New York. Russia denied the allegations and stressed that it did not seek to influence elections abroad.
