The Russian Foreign Ministry has protested to the US after a veteran senator called for Russian President Vladimir Putin to be assassinated.
Moscow officials summoned the US ambassador to Russia, John Sullivan, on Saturday and told him that Lindsey Graham’s comments would be treated as a serious crime in Russia.
The ministry said in a statement: “This is a public, terrorist appeal that is completely unacceptable.”
Ukraine invasion: Latest updates
If Washington did not unambiguously condemn the remarks and take concrete measures, it “will have a further devastating effect on Russian-American relations”, the ministry added.
Relations between the superpowers are already at a low following Western sanctions against Russia over its invasion of Ukraine.
Key developments:
• Russia continues its onslaught on Ukraine for the tenth day
• Western sanctions ‘equivalent to declaring war’, Putin claims
• Ukrainian President Volodymyr Zelenskyy criticises NATO for refusing to impose a no-fly zone
• Britons in Russia told to consider leaving if presence ‘not essential’
• The UN says the number of refugees fleeing the fighting could rise to 1.5 million this weekend
Earlier this week, Mr Graham, 66, a Republican from South Carolina, called on Twitter for someone in Russia to “take this guy out” – referring to Putin.
White House spokesperson Jen Psaki told reporters on Friday: “We are not advocating for killing the leader of a foreign country or regime change. That is not the policy of the United States.”
Anatoly Antonov, Russia’s ambassador to the US, described the call from Mr Graham, who has been a senator since 2003, as “unacceptable and outrageous”.
Kremlin spokesman Dmitry Peskov suggested alcohol may have played a part.
“Of course, these days not everyone is managing to preserve a sober mind, I would even say a sound mind,” he said.
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Mr Graham appeared unconcerned, tweeting on Saturday, after senators held talks with Ukrainian President Vlodomyr Zelenskyy that: “It is clear to me the world would be a better place if there was regime change in Russia.
“Putin is a war criminal who needs to go – at the hands of the Russian people – by any means possible.”