Secretary of State Marco Rubio on Sunday fiercely defended President Trump’s sharp turn against Ukraine’s leader, accusing President Volodymyr Zelensky of trying to derail the peace process with Russia by openly challenging Mr. Trump and Vice President JD Vance in a heated televised exchange from the Oval Office.

“What Zelensky did, unfortunately, is that he found every opportunity to try to ‘Ukraine-splain’ on every issue,” Mr. Rubio said on ABC’s “This Week.” “Then he confronts the vice president.”

Mr. Rubio was in the Oval Office when Mr. Trump and Mr. Vance launched a public attack on Mr. Zelensky on Friday after the Ukrainian president, seeking to underscore Ukraine’s need for U.S. security guarantees in any cease-fire agreement with Russia, began running through Russia’s repeated aggressions on his country since 2014.

Mr. Vance interrupted, characterizing Mr. Zelensky’s efforts to elaborate the Ukrainian perspective in front of reporters and television cameras as “disrespectful” and scolding him for not being sufficiently grateful for U.S. support. Mr. Trump, his voice raised, then accused Mr. Zelensky of “gambling with World War III.”

On Sunday, Mr. Rubio leaned heavily on emotive language to push back against the critics who have since berated the Trump administration for the public display of hostility toward Mr. Zelensky, a wartime president who frames his battle against Russia’s invasion as a bulwark of Europe’s security and freedom. Mr. Rubio said he was “puzzled” by the “absurd” pushback on the administration and said Mr. Trump was being unfairly criticized when he was trying to prevent further destruction by bringing peace to the region.

Mr. Rubio sprinkled his comments with open rebukes of Mr. Zelensky. He said that the Ukrainian president “couldn’t contain himself” and had hindered Trump’s peace effort.