WASHINGTON/KYIV: U.S. President Donald Trump denounced Ukrainian President Volodymyr Zelenskiy as a "dictator" on Wednesday and warned he had to move quickly to secure peace or risk losing his country, deepening a feud between the two leaders that has alarmed European officials.

The extraordinary attacks - a day after Trump claimed Ukraine was to blame for Russia's 2022 invasion - heightened concerns among U.S. allies in Europe that Trump's approach to ending the Russia-Ukraine conflict could benefit Moscow.

Less than a month into his presidency, Trump has upended U.S. policy on the war, ending a campaign to isolate Russia with a Trump-Putin phone call and talks between senior U.S. and Russian officials that have sidelined Ukraine.

"A Dictator without Elections, Zelenskyy better move fast or he is not going to have a Country left," Trump wrote on social media, using an alternate spelling for the Ukrainian president's name.

In response, Ukrainian Foreign Minister Andrii Sybiha said no one could force his country to give in.

"We will defend our right to exist," Sybiha said on X.

Zelenskiy's five-year term was supposed to end in 2024, but presidential and parliamentary elections cannot be held under martial law, which Ukraine imposed in February 2022 in response to Russia's invasion.

Trump's outburst followed Zelenskiy's comments on Tuesday that the U.S. president was parroting Russian disinformation when he asserted that Ukraine "should never have started" the war, which began with Russia's full-scale invasion three years ago.

U.S. Vice President JD Vance on Wednesday warned Zelenskiy against attacking Trump.

"The idea that Zelenskiy is going to change the president's mind by badmouthing him in public media ... everyone who knows the president will tell you that is an atrocious way to deal with this administration," Vance said in his West Wing office, the Daily Mail reported.

Russia has seized some 20% of Ukraine and is slowly but steadily gaining more territory in the east. Moscow said its "special military operation" responded to an existential threat posed by Kyiv's pursuit of NATO membership. Ukraine and the West call Russia's action an imperialist land grab.

The Ukrainian leader said Trump's assertion that his approval rating was just 4% was Russian disinformation and that any attempt to replace him would fail.

"We have evidence that these figures are being discussed between America and Russia. That is, President Trump ... unfortunately lives in this disinformation space," Zelenskiy told Ukrainian TV.

The latest poll from the Kyiv International Institute of Sociology, from early February, found 57% of Ukrainians trust Zelenskiy.

Following Trump's latest remarks, U.N. spokesperson Stephane Dujarric said Zelenskiy "sits in office after duly-held elections." When asked who started the war, Dujarric responded that Russia had invaded Ukraine.

German Chancellor Olaf Scholz said it was "false and dangerous" for Trump to call Zelenskiy a dictator, German newspaper Spiegel reported.

A few of Trump's fellow Republicans in Congress said they disagreed with the president's claim that Zelenskiy was a dictator and Ukraine bore responsibility for Russia's invasion. But they stopped short of criticizing Trump directly, with Senate Majority Leader John Thune - a longtime supporter of Ukraine - saying Trump needed "space" to work on a peace deal.

EUROPE LEFT SCRAMBLING

European officials have been left shocked and flat-footed by the Trump administration's moves on Ukraine in recent days.

At a second meeting of European leaders in Paris, hastily arranged by French President Emmanuel Macron earlier in the day, there were more calls for immediate action to support Ukraine and bolster Europe's defense capabilities, but few concrete decisions.

Macron and British Prime Minister Keir Starmer will visit Washington next week, amid other meetings aimed at bringing an end to Russia's war in Ukraine, according to White House national security adviser Mike Waltz.

Following Trump's latest attacks, Zelenskiy discussed approaches to a peace settlement with NATO Secretary General Mark Rutte, Macron and Starmer, including the importance of security guarantees.

Starmer expressed support for Zelenskiy as Ukraine's democratically elected leader and said it was "perfectly reasonable" to suspend elections during wartime, Starmer's office said on Wednesday.

Kellogg, the U.S. Ukraine envoy, said as he arrived in Kyiv that he understood "the need for security guarantees," adding that part of his mission would be "to sit and listen."

The 27-member European Union on Wednesday agreed on a 16th package of sanctions against Russia, including on aluminium and vessels believed to be carrying sanctioned Russian oil.

PUTIN, TRUMP WANT SUMMIT

Trump said he may meet Putin this month. In Moscow, Putin said that Ukraine would not be barred from peace negotiations, but success would depend on raising the level of trust between Moscow and Washington.

Putin, speaking a day after Russia and the U.S. met in Riyadh to hold their first talks on how to end the conflict, also said it would take time to set up a summit with Trump, which both men have said they want.

"We need to ensure that our teams prepare issues that are extremely important for both the United States and Russia, including - but not only - on the Ukrainian track, in order to reach solutions acceptable to both sides," Putin said in televised remarks.

Ukraine and European governments were not invited to Tuesday's talks in the Saudi capital, which magnified their concern that Russia and the U.S. might cut a deal that ignores their vital security interests.

Ukraine was counting on "the unity of Europe and the pragmatism of America," Zelenskiy said in a video address on Wednesday.

Trump says Europe must step up to guarantee any ceasefire deal.

Zelenskiy has suggested giving U.S. companies the right to extract valuable minerals in Ukraine in return for U.S. security guarantees, but said Trump was not offering that.