Washington(CNN) A Republican senator is calling on President Donald Trump on Monday to declare that Russia is "the enemy of America and our allies."

Sen. Ben Sasse, a Nebraska Republican, responded to Trump's tweet ahead of his meeting with Russian President Vladimir Putin in which the President said the US relationship with Russia "has NEVER been worse thanks to many years of U.S. foolishness and stupidity and now, the Rigged Witch Hunt!"

Sasse responded to Trump right as the meeting with Putin was scheduled to start.

"A better thing, Mr. President, would be to declare: 'Russia is the enemy of America and our allies, and we will expose and respond to their continued cyber-attacks against our nation.'"

Sasse has previously criticized Trump's policies toward Russia. On Sunday, the Republican senator followed the calls of several top Democrats and tweeted that the President should not be "dignifying Putin with the meeting."

"No matter how much Putin flatters the President, he is a KGB thug who jails political opponents, encourages/orders the murder of Russian dissidents and defectors at home and abroad, and who directs a military that bombs women, children, and the injured in hospitals in Syria," Sasse wrote.