The envoy's visit took place as Mr Trump launched a series of blistering attacks against the Ukrainian president in an apparent display of frustration that Mr Zelenskyy had refused to sign a deal to hand over 50% of Ukraine's natural mineral resources as part of a new economic and security partnership with the US.
Lieutenant General Keith Kellogg's comments, on a visit to a Ukrainian military hospital on Friday, are in stark contrast to the aggressive rhetoric from his boss, who has called President Volodymyr Zelenskyy a "dictator without elections" and suggested Ukraine started the war.
There are concerns among Ukrainian officials, however, that General Kellogg - who was not part of a top-level US delegation that held a landmark meeting with Russian officials in Saudi Arabia to talk about an end to the war - has been sidelined by the White House.
The US is "with" Ukraine and any deal to end the fighting with Russia should ensure there is no "next war", President Donald Trump's special envoy for Kyiv and Moscow has said.
Earlier, the retired US officer, 80, had also chosen to describe Mr Zelenskyy as "the embattled and courageous leader of a nation at war" - using very different language to Mr Trump's.
