“President Trump should have only one message for Putin tomorrow: Quit messing with America,” he added.

Sasse hit Putin for his history as a member of the KGB, the security agency for the Soviet Union, and his authoritarian rule in Russia.

“Putin is a murderer,” Sasse tweeted. “He has ordered the assassinations of political adversaries and used outlawed chemical weapons to do it.”

Sasse also called Putin a “crook and a liar” for breaking agreements with the U.S. on Syria and the Ukraine, and an “enemy of America” for attacking the U.S. “regularly.”