Outgunned Ukrainian forces have slowly lost territory to Russian troops over recent weeks. But in the capital Kyiv, the ground is shifting rapidly beneath President Volodymyr Zelensky's feet.

US President Donald Trump, his most powerful yet unpredictable ally, has called into question years of staunch support from Washington by amplifying a string of dangerous and false Kremlin propaganda talking points.

Trump described Zelensky as a corrupt "dictator" and falsely claimed he was no longer Ukraine's legitimate leader -- all as Russian troops are clawing forward across the sprawling front line.

"Zelensky is not well prepared to deal with these two challenges at once," said Silvester Nosenko, an international relations lecturer in Kyiv and former interpreter for the Ukrainian leader.

Zelensky must now race to come up with new arguments to convince Trump that Ukraine matters, he added, even as Russian and US officials press ahead with talks to lay the ground for peace.

"But there isn't much time for that," Nosenko told AFP.

Zelensky, a former comedian, won........

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