President Volodymyr Zelensky of Ukraine said that a broad overhaul of the country’s military and civilian leadership was needed to reboot the war effort against Russia, suggesting that a major shake-up of his government was imminent.

Mr. Zelensky’s comments, in a broadcast on Sunday night, indicated that his plans went beyond replacing the top military commander, Gen. Valeriy Zaluzhny. And they signaled increasing turmoil in Ukraine’s leadership at a precarious moment, with depleted Ukrainian forces on the defensive and leaders in Kyiv waiting to see whether the United States will provide much-needed military and financial assistance.

“A reset, a new beginning is necessary,” Mr. Zelensky told the Italian media outlet Rai News. “I have something serious in mind, which is not about a single person but about the direction of the country’s leadership.”

Friction between the military and the civilian government represents the most serious schism in Ukraine’s leadership since the start of the war almost two years ago. The acrimony, which has been building for months, seemed to reach a breaking point last week, when Mr. Zelensky summoned General Zaluzhny for a meeting to tell him he was being fired, according to Ukrainian officials familiar with the discussion.

Heightening the tension in Kyiv is the prospect of a new mobilization bill that could lead to the drafting of up to 500,000 troops. The bill, under debate in the Ukrainian Parliament, could be politically unpopular with the country’s war-weary citizenry.

The plans to reshuffle the civilian government signify a break with nearly two years of continuity in Mr. Zelensky’s wartime administration as he had mostly left in place ministers serving before Russia’s full-scale invasion. Before that, his government had been a swirling revolving door of ministers.