Ukrainian President Volodymyr Zelenskyy dismissed claims on Sunday that former President Trump could end the Ukraine war in 24 hours, as he has claimed, and said that President Joe Biden could end it in five minutes.

On ABC's "This Week," Zelenskyy said through a translator that the conflict has been going on through Russian proxies since Russia invaded Crimea in 2014, which means it was ongoing during Trump's first term from 2017 to 2020.

"The sole desire to bring the war to an end is beautiful, but this desire should be based on some real-life experience," Zelenskyy said. "Donald Trump had already these 24 hours once in his time. We were at war, not a full-scale war. ... (Trump) had that time at his disposal, but he must have had some other priorities."

Trump's actual plan to end the war has been vague and short on details.

Zelenskyy doubtful

Zelenskyy said that if Trump meant to end the war by forcing Ukraine to cede territory, "(President Joe) Biden could have brought it to an end even in five minutes, but we would not agree."

He said that he would never agree to give up any territory to Russia, including Crimea.

What Zelenskyy wants to see happen is for his military to push Russia back to the Crimean border, which he thinks would force Putin into negotiations.

ABC News' Chief Global Affairs Correspondent Martha Raddatz asked Biden whether he thought his plan was really feasible.

He said, "Well, it is absolutely clear, logical rhetoric that at that moment when Ukraine will reach the administrative border with a temporarily occupied Ukrainian peninsula, Crimea, it's very likely that Putin will be forced to seek dialogue with the civilized world, unlike how it was before the full-scale invasion, because he will be weakened."

America backs Ukraine

The majority of American elected officials, including Biden, back Ukraine's effort to expel Russia, and Biden has pledged to back Ukraine "for as long as it takes."

He recently gave Ukraine cluster bombs that are like those Russia has allegedly used against Ukrainian civilians earlier in the war. Ukraine does not plan to use the bombs against civilian targets.

Zelenskyy expressed concern that U.S. support would diminish, but said he didn't want to "interfere."

Members of the Council on Foreign Relations met with Russian Foreign Minister Sergey Lavrov in April to begin preparing for an end to the war, but the U.S. was not involved in the "secret" talks, National Security Council coordinator for strategic communications John Kirby said Sunday.

Five Ukrainian commanders returned home to Ukraine on Saturday after a prisoner exchange, but the return angered Russian negotiators, who had said that the commanders were to stay in Turkey until the war ended.