Munich, Germany - Ukraine's leader Volodymyr Zelensky said Saturday he was ready to take Donald Trump to the frontlines, as fears grow over sustained US aid to Kyiv should the ex-president return to the White House.

Zelensky told the Munich Security Conference he had invited Trump to Ukraine because policymakers should see what real war entailed.

"If Mr. Trump will come, I'm ready to go with him to the frontline," said the Ukrainian president.

"I think if we're in dialogue how to finish the war, we have to demonstrate to people who are decision-makers what does it mean the real war, not in Instagram. Real war," said Zelensky in English.

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The long-term future of billions of dollars of Western aid for Ukraine is in doubt, with a possible $60-billion package of military aid held up in Washington since last year because of wrangling in Congress.

A possible return by Trump to the White House has also cast a pall over the prospects of sustained US aid for Ukraine.

He has spoken out against President Joe Biden's military support for Ukraine.

During his four-year tenure as president, Trump had also voiced admiration for Russian President Vladimir Putin.

At a campaign rally this month, Trump said he would even "encourage" the Russians "to do whatever the hell they want" if a NATO member does not "pay your bills," a reference to defense spending.

Zelensky said in December that a Trump presidency would have a "very strong impact on the course of the war."

Trump has so far dominated opinion polls in the race for the Republican presidential nomination ahead of the 2024 elections but faces several criminal indictments that put him at risk of imprisonment.