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.

With American aid stalled, political analysts have suggested that Mr. Zelensky might promote Ukraine’s ambassador to the United States, Oksana Markarova, who is seen as being in favor with the Biden administration, to a senior position in Kyiv. The U.S. government has been pushing for overhauls to strengthen anti-corruption safeguards on the billions of dollars in financial and military aid Ukraine is receiving during the war.

On the battlefield, Ukrainian forces are at perhaps their weakest point since the summer of 2022. Short of ammunition and personnel, they are struggling to hold back renewed Russian offensives across the front, with the epicenter of the fighting around the battered city of Avdiivka in the eastern Donetsk region.

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A Ukrainian soldier in camouflage walks through a shoulder-deep trench in a barren forest.
A Ukrainian soldier from the 24th Mechanized Brigade in a trench in the Donetsk region last month.Credit…Tyler Hicks/The New York Times

Russian soldiers, using heavy cloud cover to evade detection by Ukrainian surveillance drones, managed to break into the northern outskirts of the city in recent days, according to Ukrainian soldiers in the area.

They are increasingly threatening a vital supply line and Ukraine’s control over the city. The fall of Avdiivka would represent the Russian forces’ most significant victory since they took Bakhmut in May, and it would open up new lines of assault in the Kremlin’s bid to seize the entire eastern Donbas region.

E.U. leaders have agreed to create a 50-billion-euro fund to support Kyiv against Moscow and help alleviate a potentially severe financial crisis in Ukraine.

It could also free up resources for another Russian push taking place several hundred miles to the north, in the Kharkiv region.

Moscow has amassed more than 40,000 troops and hundreds of tanks and armored vehicles near Kupiansk, part of what Ukrainian military commanders said is an intensifying bid to retake territory in Kharkiv that Russian forces lost in a Ukrainian offensive more than a year ago.

The Ukrainian defense has been hindered by the suspension of vital American military assistance, with Republican lawmakers in the House of Representatives blocking repeated efforts to provide new funding.

The lack of assistance has not only resulted in a critical shortage of artillery and other weapons, but has made planning for the future exceedingly difficult.

A self-propelled howitzer fires a round at dusk from a stand of trees, with flames from the discharge lighting up the sky.
A Ukrainian tank firing on Russian troops near Kupiansk, a town in the Kharkiv region, in December.Credit…Viacheslav Ratynskyi/Reuters

Even before the impasse in Washington, newly committed aid to Ukraine had dropped almost 90 percent between August and October compared with the same period in 2022, according to the Kiel Institute for the World Economy, a German research institute.

While Senate Republicans and Democrats on Sunday unveiled a $118.3 billion bill that tied $60 billion in security aid for Ukraine to assistance for Israel as well as U.S. border security reforms, Speaker Mike Johnson, who had insisted on linking the disparate issues, has said the bill would be “dead on arrival” in the Republican-controlled House.

Former President Donald J. Trump is campaigning against the deal and is pressuring his supporters in Congress to block it.

Mr. Biden urged lawmakers on Sunday to pass the legislation, saying that “if we don’t stop Putin’s appetite for power and control in Ukraine, it will go beyond Ukraine, and the cost to America will rise.”

President Volodymyr Zelensky of Ukraine, in  military fatigues, with President Biden at the White House, with presidential portraits behind them.
President Biden and Mr. Zelensky in the Oval Office in September.Credit…Doug Mills/The New York Times

Mr. Zelensky’s frustrations with General Zaluzhny have grown over the past year, as the fighting has bogged down in bloody, static trench warfare. But Mr. Zelensky has moved cautiously.

Replacing the military’s commanding general amid a Russian offensive along nearly the entire eastern front carries risks, as General Zaluzhny is well-regarded by soldiers and junior officers. His removal would be the most significant change in military leadership after the invasion.

“Soldiers see in him a leader, him and nobody else,” said an army major who asked to be identified only by his first name, Bohdan. Other officers have said that the army, respectful of hierarchy, would adapt quickly.

The general’s dismissal could also fuel concerns about instability in Kyiv’s wartime leadership and would almost certainly be used by Russian propagandists to depict Mr. Zelensky as an undemocratic tyrant.

After General Zaluzhny, the highest-profile military leaders in Ukraine are Gen. Kyrylo Budanov, the head of the military intelligence agency, and General Oleksandr Syrsky, the commander of ground forces.

Mr. Zelensky may be trying to mute the potential backlash against firing General Zaluzhny by positioning it as just one move among a broader realignment.

“When we talk about this, I mean a replacement of a series of state leaders, not just in a single sector like the military,” Mr. Zelensky said in the broadcast on Sunday, when asked about reports that he planned to replace General Zaluzhny. “If we want to win, we must all push in the same direction, convinced of victory.”

A woman in a dark overcoat, her back to the camera, looks at a graffiti portrait of the Ukrainian general Valery Zaluzhny.
Graffiti depicting General Zaluzhny in December 2022 in the city of Bakhmut, months before it fell to Russia. It reads, “God is with us and Commander Zaluzhny.” Credit…Andriy Andriyenko/Associated Press

Jake Sullivan, the U.S. national security adviser, said that the White House had been consulted about possible changes in Ukraine’s leadership and would not weigh in on personnel decisions.

“It’s the sovereign right of Ukraine and the right of the president of Ukraine to make his personnel decisions.” he said on CBS’s “Face the Nation.” “We’ve been clear, we’re just not going to get embroiled in that particular decision. We have indicated that directly to the Ukrainians.”

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