KIEV, Ukraine (AP) — A showdown looms in Ukraine after Russia appointed a new military commander and looked to concentrate its attacks in the east, while Ukraine’s president said his troops will hold their ground, urging Western leaders, in particular President Biden, to do more.

President Zelensky warned Sunday in a nightly address that this week will be as crucial as any during the war, saying “Russian troops will move to even larger operations in the east of our state.”

Ukraine’s fate as the war shifts south and east depends on whether America will help match a surge in Russian weaponry, he said, echoing comments he made in an interview with The Associated Press on Saturday.

“To be honest, whether we will be able to (survive) depends on this,” Mr. Zelensky said in a “60 Minutes” interview. “Unfortunately, I don’t have the confidence that we will be receiving everything we need.”

Mr. Zelensky said he was grateful to Mr. Biden for American military aid to date but added that he “long ago” forwarded a list of specific items Ukraine desperately needed.

“He has the list,” Mr. Zelensky said. “President Biden can enter history as the person who stood shoulder to shoulder with the Ukrainian people who won and chose the right to have their own country. (This) also depends on him.”

Austria’s chancellor, Karl Nehammer, was due to meet Monday in Moscow with President Putin, after meeting with Mr. Zelensky in Kiev. Austria, a member of the European Union, is militarily neutral and not a member of NATO.

Also Monday, New Zealand’s prime minister, Jacinda Ardern, said it was sending a military transport plane and a support team of 50 to Europe to carry much-needed equipment and supplies to key distribution centers.

More than six weeks of war in Ukraine has flattened cities, killed untold thousands and isolated Moscow economically and politically, and experts say the next phase of the battle may begin with a full-scale offensive that could determine the course of the conflict.

Questions remain about the ability of depleted and demoralized Russian forces to conquer much ground after their advance on the capital, Kiev, was repelled by determined Ukrainian defenders. Britain’s Defense Ministry says Russia is trying to compensate for mounting casualties by recalling veterans discharged in the past decade.

In his Sunday night address, Mr. Zelensky also accused Russia of trying to evade responsibility for war crimes in Ukraine.

“When people lack the courage to admit their mistakes, apologize, adapt to reality and learn, they turn into monsters. And when the world ignores it, the monsters decide that it is the world that has to adapt to them,” Mr. Zelensky said.

“The day will come when they will have to admit everything. Accept the truth,” he added.

Ukrainian authorities accuse Russian forces of committing war crimes against civilians, including airstrikes on hospitals, a missile attack that killed at least 57 people at a train station and other violence.

In another report of atrocities, the village of Buzova outside the capital, Kiev, charred vehicles and buildings marked an area where local official Taras Didych told Ukrainian media Sunday that bodies showing “evidence of execution” were found after Russian forces withdrew from the region. It was unclear how many bodies were discovered.

Buzova is near Bucha, another of the towns near Kiev, where hundreds of bodies, many with their hands bound and signs of torture, were found after the Russian retreat. Russia has falsely claimed the scenes in Bucha were staged.

In Washington, a senior American official said Russia has appointed General Alexander Dvornikov, one of its most seasoned military chiefs, to oversee the invasion. The official was not authorized to be identified and spoke on condition of anonymity.

Until now, Russia has had no central war commander on the ground.

General Dvornikov, 60, takes over as the Russian military prepares to focus on expanding control in Ukraine’s east, where Russia-backed separatists have fought Ukrainian forces in the Donbas region since 2014, declaring some areas independent.

He gained a record for brutality as head of Russian forces deployed to Syria in 2015 to back President Bashar Al-Assad’s government during the country’s devastating civil war.

Russian authorities do not generally confirm such appointments and have said nothing about a new role for General Dvornikov, who received the esteemed Hero of Russia medal from President Vladimir Putin in 2016.

National security adviser Jacob Sullivan, speaking Sunday on CNN’s “State of the Union,” played down the appointment’s significance.

“What we have learned in the first several weeks of this war is that Ukraine will never be subjected to Russia,” Mr. Sullivan said. “It doesn’t matter which general President Putin tries to appoint.”

Western military analysts say Russia’s assault increasingly is focusing on a sickle-shaped arc of eastern Ukraine — from Kharkiv, Ukraine’s second-largest city, in the north to Kherson in the south.

That could counter Russia’s earlier problem of spreading its offensive too widely over too broad a geographic area.

Newly released Maxar Technologies satellite imagery showed an 8-mile convoy of military vehicles headed south through Ukraine to Donbas, recalling images of the convoy that stalled outside Kiev before Russia gave up trying to take the capital.

On Sunday, Russian forces shelled government-controlled Kharkiv and sent reinforcements toward Izyum to the city’s southeast to try to break Ukraine’s defenses, the Ukrainian military command said. The Russians also kept up their siege of Mariupol, a key southern port that has been under attack and surrounded for nearly 1 ½ months.

The Institute for the Study of War, an American think tank, predicted that Russian forces will “renew offensive operations in the coming days” from Izyum, a town southeast of Kharkiv, in the campaign to conquer the Donbas, which comprises Ukraine’s industrial heartland.

But in the view of the think tank’s analysts, “The outcome of forthcoming Russian operations in eastern Ukraine remains very much in question.”

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Cara Anna at Bucha, Ukraine, Yesica Fisch at Borodyanko, Ukraine, Robert Burns and Calvin Woodward at Washington, D.C., and Associated Press journalists around the world contributed to this report.