Latest Russia-Ukraine War News: Live Updates

Mr. Zelensky said that Russia had thwarted an initial attempt to end the war through dialogue and that now the conflict was “very difficult.” Speaking on the third anniversary of his inauguration as president, he said that the war “will be bloody” but “the end will definitely be in diplomacy.”

Despite a recent string of setbacks and a shortage of manpower and equipment, Russia pressed ahead with its military campaign in eastern Ukraine, and with its propaganda offensive at home, hours after claiming to have achieved complete control of the port city of Mariupol, in what would be its most significant gain since the war started.

Russia said in a statement late Friday that its defense minister, Sergei K. Shoigu, had informed President Vladimir V. Putin of the “complete liberation” of the Mariupol steel plant where Ukrainian fighters had made their last stand in the city before surrendering in recent days. Ukrainian officials have not confirmed the Russian claim.

The Ukrainian military, for its part, said that in the past day it had repulsed 11 attacks in the provinces of Donetsk and Luhansk, collectively known as the Donbas region, and had destroyed eight tanks as well as other Russian combat vehicles.

Overall, Mr. Zelensky asserted, Ukraine has “broken the backbone of the largest, or one of the strongest, armies in the world.”

The war is now set to enter its fourth month, and while Moscow has been forced to retreat first from outside the capital, Kyiv, and more recently from the country’s second-largest city, Kharkiv, neither side is currently making more than incremental gains.

With the conflict coming ever closer to a stalemate and both sides fighting in the Donbas region to gain the upper hand, calls for a cease-fire have grown louder, along with questions about what would constitute victory, or at least a suitable outcome, for Ukraine.

“A cease-fire must be achieved as soon as possible,” the Italian prime minister, Mario Draghi, urged on Thursday, opening a parliamentary debate on Italy’s role in backing Ukraine. He added that “we have to bring Moscow to the negotiating table.”

German, French and Italian suggestions of a cease-fire have been rejected angrily and even bitterly by Kyiv as selfish and poorly timed. Ukrainian officials say that Russia is hardly ready for serious peace talks and that their forces — despite considerable losses in the Donbas and in Mariupol — have the momentum in the war.

For now, some in Ukraine are insisting that the only outcome it will abide is the restoration of all territory lost to Russia since 1991, when it gained independence from the Soviet Union. That would include both the Donbas in its entirety and Crimea, which Russia annexed in 2014. But Mr. Zelensky has hinted that he would accept the status quo ante before the war.

Western diplomats maintain that this is a matter for Ukraine to decide. But their unanimity begins to break down when it turns to specifics.

On Friday, the U.S. ambassador to NATO, Julianne Smith, speaking at a conference in Warsaw, restated the United States’ firm support of Ukraine. “In terms of the end state,” she added, “we believe we will see Ukraine prevail, and we want them to protect their territorial integrity and their sovereignty.”

But she added another objective: “We want to see a strategic defeat of Russia. We want to see Russia leave Ukraine.”

For Eastern European and Baltic leaders, a durable peace settlement and an end to the conflict has to include a crushing military victory that spells an end to Mr. Putin’s presidency. Anything short of his departure would merely pave the way for the next war, they say. They balk at suggestions from Berlin, Paris and Rome to lure Mr. Putin back to the negotiating table.

“Peace can’t be the ultimate goal,” Prime Minister Kaja Kallas of Estonia recently told The New York Times. “I only see a solution as a military victory that could end this once and for all, and also punishing the aggressor for what he has done.”

Otherwise, she said, “we go back to where we started — you will have a pause of one year, two years, and then everything will continue.”

“All these events should wake us from our geopolitical slumber, and cause us to cast off our delusions,” Prime Minister Mateusz Morawiecki of Poland said on Thursday at the Warsaw conference. “I hear there are attempts to allow Putin to somehow save face in the international arena. But how can you save something that has been utterly disfigured?”

“Russia can only be deterred by our unity, military capabilities and hard sanctions,” he added. “Not by phone calls and conversations with Putin.”

In a diplomatic salvo of its own, Russia’s Foreign Ministry on Saturday released a list of 963 people who would be barred for life from entering Russia, among them Mr. Biden, the actor Morgan Freeman and the New York Times columnist Bret Stephens. The ministry described its move as “necessary” retaliation against the “hostile actions” of the United States.

Against the backdrop of an unfolding debate about what a final settlement might look like, Russian and Ukrainian forces dug in on the battlefield, conscious that every military victory would turn into a diplomatic advantage.

The Ukrainian military said on Saturday that Russia was demining the port of Mariupol in an attempt to get it running again. Reopening the port would tighten Moscow’s control over the parts of southern and eastern Ukraine that it controls, as well as increase its economic leverage over the Black Sea, where its navy is dominant.

And Russian forces have become entrenched in areas outside of the city of Kharkiv, presenting a formidable obstacle to any Ukrainian efforts to press their advantage in that area.

Russia’s military prepared on Saturday to attempt another pontoon crossing of an eastern Ukrainian river that has posed a formidable barrier to its aims in the region, Ukraine’s military said, despite suffering one of its single most lethal engagements of the war in a previous attempt this month.

Russian forces were staging bridging equipment again near the Seversky Donets River, the Ukrainian military said in its regularly published morning assessment of the war. The stream’s winding path cuts through the heart of the region where Russian forces are battling Ukrainian defenders — around the cities of Izium, Sloviansk, Kramatorsk and Sievierodonetsk — creating major obstacles to Moscow’s offensive in eastern Ukraine.

“The enemy has not ceased offensive actions in the eastern operation zone with the goal of establishing full control over the territory of the Donetsk and Luhansk regions,” the assessment said.

Ukraine’s military has blown up bridges to force the Russians to build pontoon bridges, a tactic that has proved effective — and costly for the Russian army. Military forces are particularly vulnerable to artillery strikes as they congregate soldiers, armored vehicles and equipment while attempting a crossing.

In the battle for control of the Donbas region, Russian forces have attempted several pontoon crossings of the Seversky Donets, seen as an important tactical step toward the goal of surrounding a pocket of Ukrainian troops in and around the city of Sievierodonetsk.

On May 11, Ukrainian artillery struck a pontoon crossing with devastating effect, destroying the bridge, incinerating armored vehicles on both river banks and killing more than 400 soldiers, according to estimates by Western military analysts. The British Defense Ministry has issued statements corroborating the Ukrainian accounts, based on satellite imagery and aerial drone imagery posted online of the strike.

Whatever the ultimate outcome of the war, no one expects it to end soon, as each country’s leader needs to be able to claim some sort of victory, particularly Mr. Zelensky.

“For Zelensky, there is no other path forward than to continue to fight and reconquer the territory they lost,” said Andrew A. Michta, a German-based foreign policy and defense analyst. “The minute he agrees to any compromise, given the blood paid, he loses political credibility. The Ukrainians can’t cut a deal just to stop the fighting, so this will be a long, drawn-out war.”

Steven Erlanger reported from Warsaw, Andrew E. Kramer from Dnipro, Ukraine, and Katrin Bennhold from Berlin. Anton Troianovski contributed reporting from Istanbul.