US President Joe Biden called Russian President Vladimir Putin a “butcher” and said “this man cannot stay in office” during speeches he made in Warsaw over the weekend, comments that worried the US’ European allies as going too far.

Whilst in a stadium to meet Ukrainian refugees from the war there, Biden was asked by reporters what seeing the Ukrainian refugees at Stadion Narodowy made him think of. Biden responded: "He's a butcher."

Biden later made a speech, closing with a comment that Vladimir Putin could not "remain in power." It was later reported that this comment was off the cuff and not part of the prepared speech.

The comments have unsettled European allies and political analysts warned that they would be used to fuel Kremlin propaganda and paranoia that the US is seeking regime change in Russia.

Macron said in comments later in the day that he didn't think it was wise to label Putin a butcher.

“I wouldn’t use terms like that because I’m still in talks with President Putin,” the French President said during an interview. Other political analysts warned the comment could lead to Russia breaking off diplomatic relations with the US completely.

Last week, Biden for the first time called Putin a "war criminal" and then later referred to him as a "murderous dictator, a pure thug who is waging an immoral war against the people of Ukraine." He's also called the Russian invasion of Ukraine "inhumane".

The Russian Foreign Ministry reacted very strongly to Biden’s “thug” comment, saying it was a major breach of diplomatic protocol.

The “he can’t stay in power” comment had the White House rapidly backtracking, to try to contain speculation that the US would use the war in Ukraine to change the regime in Russia.

Author and academic Niall Ferguson said in a tweet: “As I said last week, the Biden administration has apparently decided to instrumentalise the war in Ukraine to bring about regime change in Russia, rather than trying to end the war in Ukraine as soon as possible. Biden just said it out loud. This is a highly risky strategy.”

Within hours of Biden’s speech the White House issued a “clarification”, saying the president was “making the point that Putin cannot be allowed to exercise power over his neighbours or the region”.

The speech was delivered to a large crowd, as Poland has been the main destination for some 2mn of the 3.5mn Ukrainians that have fled the fight and they have been greeted with a warm welcome by the Polish population.

Biden reiterated that the US “stands by Ukraine” and has rapidly increased its weapons supplies to bolster Ukraine’s resistance to the Russian invaders.

“In the year before the invasion, America had sent $650mn in weapons to Ukraine – and since then, we have committed to another $1.35bn,” Biden said. “Thanks to the courage and bravery of the Ukrainian people, the equipment we have sent them has been used to devastating effect.”

Ukrainian President Volodymyr Zelenskiy has welcomed the military aid, but has repeatedly lambasted Nato for not sending heavier and more sophisticated weapons such as fighter jets or surface-to-air missiles (SAMs).

Outside the conference hall where Biden was speaking a lone Ukrainian refugee told a crowd that “talk is not enough” and that “Ukraine needs weapons, more weapons. We are not asking for Nato’s help or its soldiers. We need arms to fight against Russia.”