Kremlin: Russian-U.S. relations 'on the verge of breaking' after Biden called Putin a 'war criminal'

Russia's Ministry of Foreign Affairs on Monday told the U.S. ambassador in Moscow that President Joe Biden's comments about Russian President Vladimir Putin have brought relations between the two countries to "the verge of breaking."

U.S. Ambassador to Russia John Sullivan was "summoned" to the Foreign Ministry, where he "was demarched and handed a note of protest in connection with the recent unacceptable statements made by the head of the White House, Joe Biden, to the President of Russia," according to a translated Russian government press release.

Last week, Biden said he thinks Putin is a "war criminal." At another event later that week, Biden called Putin a "murderous dictator" and "pure thug who is waging an immoral war against the people of Ukraine."

During the Monday meeting, the Kremlin "emphasized that such statements by the American President, unworthy of a statesman of such a high rank, put Russian-American relations on the verge of breaking," according to the Foreign Ministry's press release.

"They warned that hostile actions taken against Russia would receive a decisive and firm rebuff," the ministry stated.

The U.S. Embassy in Moscow said that during the meeting, Ambassador Sullivan "demanded that the government of Russia follow international law and basic human decency to allow consular access to all U.S. citizen detainees in Russia, including those in pre-trial detention."

The U.S. Embassy also said Sullivan condemned Russia's treatment of American citizens.

"We have repeatedly asked for consular access to American citizen detainees and have consistently and improperly been denied access for months. This is completely unacceptable," the embassy said.

Russia's Foreign Ministry stressed importance of continuing business as usual.

Sullivan "was acutely confronted with the issue of ensuring normal working conditions for Russian diplomatic missions in the United States, including guarantees for their uninterrupted functioning," the agency stated.

Kremlin spokesman Dmitry Peskov responded to Biden's remarks against Putin last week by criticizing the former as forgetful and tired.

"Given Mr. Biden’s irritability, his fatigue and sometimes forgetfulness ... which ultimately leads to aggressive statements, we probably will not give any sharp assessments so as not to cause more aggression," Peskov said, according to The Washington Post.

Russia's invasion of Ukraine aside, the meeting comes at a particularly tense time for diplomats from Russia and the United States. 

The Biden administration announced the expulsion of 12 Russian diplomats late last month over national security threats unrelated to Putin's invasion of Ukraine. 

Russia's second-highest diplomat in the U.S. was also expelled from America last month in response to the Kremlin's expulsion of the U.S.'s second-ranking diplomat.