Trump warns Zelenskiy to rush for peace or lose Ukraine

US President Donald Trump has denounced Ukrainian President Volodymyr Zelenskiy as "a dictator without elections" and says he had better move fast to secure peace or he will have no country left.

Trump spoke hours after Zelenskiy hit back at his suggestion that Ukraine was responsible for Russia's 2022 full-scale invasion, saying the US president was trapped in a Russian disinformation bubble.

"A Dictator without Elections, (Zelenskiy) better move fast or he is not going to have a Country left," Trump wrote on social media on Wednesday.

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 elections cannot be held under martial law, which Ukraine imposed in February 2022 in response to Russia's invasion.

Zelenskiy, who met Trump's Ukraine envoy Keith Kellogg in Kyiv on Wednesday, said he would like Trump's team to have "more truth" about Ukraine, a day after Trump said Ukraine "should never have started" the conflict with Russia.

The Ukrainian leader said Trump's assertion that his approval rating was just four per cent was Russian disinformation, and 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 says 57 per cent of Ukrainians trust Zelenskiy.

Less than a month into his presidency, Trump has upended US policy on Ukraine and Russia, ending Washington's bid to isolate Russia over the invasion with a Trump-Putin phone call and talks between senior US and Russian officials.

Following Trump's remarks, UN spokesman 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.

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, there were more calls for immediate action to support Ukraine and bolster Europe's defence capabilities, but few concrete decisions.

Macron and British Prime Minister Keir Starmer will visit Washington next week.

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

Trump said he might meet Putin later in February.

In Moscow, Putin said Ukraine would not be barred from peace negotiations but success would depend on increasing trust between Moscow and Washington.

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

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

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

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

Zelenskiy told reporters the US had given Ukraine $US67 billion ($A105 billion) in weapons and $US31.5 billion in budget support, and American demands for $US500 billion in minerals were "not a serious conversation", and he could not sell his country.

Kellogg, the US Ukraine envoy, said as he arrived in Kyiv that he expected substantial talks.

"We understand the need for security guarantees," Kellogg told reporters, adding that part of his mission would be "to sit and listen".

Trump's US policy reversal clashed with allies in the 27-member European Union, whose envoys on Wednesday agreed on a 16th package of sanctions against Russia, including on aluminium and vessels believed to be carrying sanctioned Russian oil.