The cracks in Donald Trump and Volodymyr Zelenskyy's relationship became chasms on Wednesday after the US president accused his Ukrainian counterpart of being a "dictator" and "doing a terrible job".
In a post published to his Truth Social platform, Mr Trump described Mr Zelenskyy as a "modestly successful comedian" who had played Joe Biden, his predecessor in the White House, "like a fiddle".
The US president used the post to again criticise the amount of money his country had spent arming Ukraine, which has been fighting Russia's invading forces for nearly three years.
He also said Mr Zelenskyy needed to "move fast" or he would lose his country.
In his nightly video address, the Ukrainian president did not respond directly to Mr Trump's barb, but said: "We are standing strong on our own two feet. I am counting on Ukrainian unity, our courage … on the unity of Europe and the pragmatism of America."
Mr Trump's Truth Social post came less than 24 hours after he used a press conference at his Mar-a-Lago mansion in Florida to criticise Ukraine's leader.
In that diatribe, he falsely claimed that Mr Zelenskyy's approval rating was at 4 per cent and that he should hold elections.
That was on Tuesday, local time, and the next day, Ukraine's leader hit back, accusing Mr Trump of living in a Russian "disinformation space".
Since his inauguration last month, Mr Trump has steadily reshaped US foreign policy to be more sympathetic to Moscow, and earlier this week even went as far as repeating a Kremlin lie that Ukraine was responsible for starting the war.
He's repeatedly insisted that the conflict must end as soon as possible, and that he's the only person capable of brokering a peace deal.
The US president's social media spray was delivered as his envoy to Ukraine, Keith Kellogg, arrived in Kyiv for talks with Mr Zelenskyy, who has criticised the new US administration's approach to ending the war.
Mr Kellogg told Ukrainian public broadcaster Suspilne Novyny: "It's very clear to us the importance of the sovereignty of this nation and the independence of this nation as well."
In his video address on Wednesday evening, Mr Zelenskyy said he was counting on "constructive" dialogues with Mr Kellogg.
After Mr Trump's Truth Social rant, Ukraine's foreign minister, Andrii Sybiha, posted on X that his country would "defend our right to exist".
"Ukraine withstood the most horrific military attack in Europe's modern history and three years of a total war. The Ukrainian people and their president refused to give in to Putin's pressure. Nobody can force Ukraine to give up," he wrote.
German Chancellor Olaf Scholz told German media that calling Mr Zelenskyy a dictator was "simply wrong", adding it was "dangerous to deny President Zelenskyy his democratic legitimacy".
British Prime Minister Keir Starmer phoned the Ukrainian president on Wednesday evening to support the country's "democratically elected leader", according to a statement from his office.
Sir Keir told his counterpart that it was "perfectly reasonable to suspend elections during war time as the UK did".
The latest poll from the Kyiv International Institute of Sociology, from early February, says 57 per cent of Ukrainians trust their president.
In November last year, all parties in Ukraine's parliament voted to suspend elections in the country until after the end of the war. Mr Zelenskyy himself has vowed to hold polls in the country once the fighting stops.
Earlier this week, US and Russian officials met for the first official in-person talks between the two nuclear-armed powers since the war began.
European leaders, as well as Mr Zelenskyy, were excluded from the summit.
That saw French President Emmanuel Macron host some European leaders in Paris on Monday in an attempt to forge a coordinated continental response.
He held another meeting on Wednesday, local time, with 19 other countries.
Mr Trump's social media post will alarm Ukraine and its allies, who've been growing concerned about the US president's deteriorating rhetoric surrounding Kyiv and relationship with Russian leader Vladimir Putin.
The US president has already floated the idea of offering several major concessions to Russia over the past fortnight, including cutting aid to Ukraine and denying its bid for NATO membership, and encouraging Kyiv to cede territory to Russia.
Mr Zelenskyy has maintained that he will not agree to any peace deal that is negotiated without his country being at the table.