Lt Gen Kellogg's trip to Kyiv coincided with recent feuding between Mr Trump and Mr Zelenskyy that has cast further doubt on the future of US support for Ukraine's war effort.
His comments were in response to Mr Zelenskyy accusing his US counterpart of living in a "disinformation bubble" after Mr Trump blamed Ukraine for the war.
When asked if Mr Trump blames Russia or Ukraine for the war - which was launched by Moscow in February 2022 - Mr Waltz would not give a direct answer.
He went on to insist Mr Trump is the best person to negotiate with Russia's Vladimir Putin, despite concerns the US will force Ukraine into concessions after kicking off talks this week without Europe or Kyiv.
French President Emmanuel Macron, who is due to meet with Mr Trump in Washington on Monday, said he would tellthe president not to be "weak" on Mr Putin.
