The Kremlin said U.S. President Joe Biden as "a state leader should keep their temper" after Biden called his Russian counterpart Vladimir Putin "a butcher."

"And, of course, each time such personal insults narrow the window of opportunity for our bilateral relations under the current (U.S.) administration. It is necessary to be aware of this," Kremlin spokesperson Peskov Dmitry told Russia's TASS news agency about Biden's new comments, which were made during his visit to Poland on Saturday.

The U.S. president has previously described Putin as a "murderous dictator" and a "pure thug," as well as a "war criminal." 

And the Russian foreign ministry has warned that Biden's remarks about Putin have put the two countries' bilateral relationship on the verge of breaking down.

On Friday, head of Russia's negotiation team Vladimir Medinsky said