KYIV, Ukraine >> A showdown looms in Ukraine after Russia appointed a new military commander and looked to concentrate its attacks on the eastern part of the country, while Ukraine’s president said his troops will hold their ground, urging Western leaders, in particular U.S. President Joe Biden, to do more.

Ukrainian President Volodymyr Zelenskyy warned Sunday in his nightly address to the nation 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 the United States will help match a surge in Russian weaponry, he said.

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

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

“He has the list,” Zelenskyy 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.”

Austrian Chancellor Karl Nehammer was due to meet Monday in Moscow with Putin, after meeting with Zelenskyy in Kyiv. Austria, a member of the European Union, is militarily neutral and not a member of NATO.

Experts say the next phase of the battle may begin with a full-scale offensive whose outcome could determine the course of the conflict, which has flattened cities, killed untold thousands and isolated Moscow economically and politically.

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

In his Sunday night address, Zelenskyy 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,” Zelenskyy said.

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

In Washington, a senior U.S. official said that Russia has appointed Gen. 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.

Dvornikov, 60, takes over as Russian military prepares to focus on expanding control in Ukraine’s east. Russia-backed separatists have fought Ukrainian forces in the eastern Donbas region since 2014 and declared some territory there independent.

He gained prominence as head of Russian forces deployed to Syria in 2015 to back President Bashar Assad’s government during the country’s devastating civil war. U.S. officials say he has a record of brutality against civilians in Syria and elsewhere.

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

U.S. national security adviser Jake 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,” 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.

“Just looking at it on a map, you can see that they will be able to bring to bear a lot more power in a lot more concentrated fashion,” by focusing mainly on eastern Ukraine, Pentagon spokesman John Kirby said Friday.

Newly released Maxar Technologies satellite imagery showed an 8-mile (13-kilometer) convoy of military vehicles headed south through Ukraine to Donbas, recalling images of a convoy that got stalled on roads to Kyiv for weeks before Russia gave up on trying to take the capital.

On Sunday, Russian forces shelled government-controlled Kharkiv and sent reinforcements toward Izyum to the 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.

A Russian Defense Ministry spokesman, Maj. Gen. Igor Konashenkov, said Russia’s military used air-launched missiles to hit Ukraine’s S-300 air-defense missile systems in the southern Mykolaiv region and at an air base in Chuhuiv, a city not far from Kharkiv.

Sea-launched Russian cruise missiles destroyed the headquarters of a Ukrainian military unit stationed farther west in the Dnipro region, Konashenkov said. Neither the Ukrainian nor the Russian military claims could be independently verified.

Missiles twice struck the airport in Dnipro, Ukraine’s fourth-largest city, on Sunday, the regional governor said.

On Sunday night, Zelenskyy again appealed for more assistance. Speaking with German Chancellor Olaf Scholz, he said he discussed “how to strengthen sanctions against Russia and … force Russia to seek peace.”

“I am glad to note that the German position has recently changed in favor of Ukraine. I consider it absolutely logical,” Zelenskyy said.

The president of the European Commission said on CNN’s “State of the Union” that Ukraine’s response to a questionnaire she gave Zelenskyy will help her decide whether to recommend the nation as a candidate to join the EU.

The process normally takes years, but Ursula von der Leyen said Ukraine’s application could take just weeks to consider.

“Yesterday, somebody told me: ‘You know, when our soldiers are dying, I want them to know that their children will be free and be part of the European Union,’” von der Leyen said.

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.

Ukraine has blamed Russia for killing civilians in Bucha and other towns outside the capital where hundreds of bodies, many with their hands bound and signs of torture, were found after Russian troops retreated. Russia has denied the allegations and falsely claimed that the scenes in Bucha were staged.

In Mariupol, Russia deployed Chechen fighters, reputed to be particularly fierce. Capturing the city on the Sea of Azov would give Russia a land bridge to the Crimean Peninsula, which Russia seized from Ukraine eight years ago.

The city’s residents have lacked food, water and electricity since Russian forces surrounded the city and frustrated evacuation missions. Ukrainian authorities think an airstrike on a theater that was being used as a bomb shelter killed hundreds of civilians, and Zelenskyy has said he expects more evidence of atrocities to be found once Mariupol no longer is blockaded.

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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Anna reported from Bucha, Ukraine. Yesica Fisch in Borodyanko, Robert Burns and Calvin Woodward in Washington, and Associated Press journalists around the world contributed to this report.