In a recent interview with the BBC, Zelenska said that "if the world gets tired" of supporting Ukraine, "they will simply let us die."
She was speaking hours after a Russian missile attack and a day after Republican senators in the United States blocked a key aid bill, the BBC reported.
Nearly two years since Russia's invasion of Ukraine, the first lady expressed grave concern over delays in funding, the BBC said on its website.
Zelenska told the BBC's Laura Kuenssberg, as quoted by the British public broadcaster: "We really need the help. In simple words, we cannot get tired of this situation, because if we do, we die. And if the world gets tired, they will simply let us die."
The Ukrainian first lady said: "It hurts us greatly to see the signs that the passionate willingness to help may fade. It is a matter of life for us. Therefore, it hurts to see that."
US President Joe Biden has said that failing to agree Ukraine aid would be a "gift" for Russian President Vladimir Putin, warning that history would "judge harshly those who turned their back on freedom's cause," the BBC reported.
Earlier this year, Zelenska was named among the world's 100 most influential people this year by Time magazine.
US First Lady Jill Biden said at the time that the wife of Ukrainian President Volodymyr Zelensky has "become the heart of a nation at war" and "a warrior for the people of Ukraine."
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Source: PAP, BBC