President Joe Biden on Wednesday updated Ukrainian President Volodymyr Zelenskyy on ongoing efforts the United States is making to provide Ukraine with additional military support, according to the White House.

Biden and Zelenskyy spoke by phone for nearly an hour.

The call comes as the White House is expected to announce as early as Wednesday afternoon an additional military assistance package to Ukraine that could be as much as $750 million and include a range of new military hardware.

During his latest national address, Zelenskyy said they spoke about the package, as well as "the prosecution of all Russian servicemen and commanders who committed war crimes" and international cooperation for such prosecution.

-ABC News' Molly Nagle

The Armed Forces of the Russian Federation is threatening strikes against Ukrainian "decision-making centers," including those in the capital of Kyiv, if alleged Ukrainian attacks and sabotage on Russian territory do not stop.

"We see attempts of sabotage and strikes by Ukrainian forces against facilities on Russian Federation territory," the Russian military said in its daily update of its "special military operation" in Ukraine. "If such cases continue, the Russian Armed Forces will strike at decision-making centers, including in Kyiv, from which the Russian army has so far refrained."

In its statement, the Russian Armed Forces claimed to have destroyed 36 enemy assets on Wednesday, including two repair bases, two missile-artillery weapon depots and the command post for the 15th Separate Regiment of the Ukrainian National Guard.

U.S. Treasury Secretary Janet Yellen is pressuring China to convince Russia to end its war in Ukraine, citing the "special relationship" between the two countries.

“I fervently hope that China will make something positive of this relationship and help to end this war," Yellen said Wednesday during remarks to the Atlantic Council.

Despite a virtual meeting between President Joe Biden and Chinese President Xi Jinping back in March to discuss the crisis in Ukraine, China has remained neutral during the Russian invasion and has refused to openly condemn Russian President Vladimir Putin. U.S. officials have said that it does not appear China has assisted with Moscow’s requests for military and economic help.

"Going forward, it will be increasingly difficult to separate economic issues from broader considerations of national interest, including national security," Yellen said. "The world’s attitude towards China and its willingness to embrace further economic integration may well be affected by China’s reaction to our call for resolute action on Russia."

Yellen noted that Beijing claims to respect sovereignty and territorial integrity and said now is the time for China to put some weight behind their commitments.

"China cannot expect the global community to respect its appeals to the principles of sovereignty and territorial integrity in the future if does not respect these principles now when it counts," Yellen said.

China and India have continued to do business with Russia despite the international condemnation of Putin’s invasion and severe sanctions by the United States and its Western allies.

Yellen warned that any assistance to help Russia undermine or evade sanctions will not be taken lightly.

"Let me now say a few words to those countries who are currently sitting on the fence, perhaps seeing an opportunity to gain by preserving their relationship with Russia and backfilling the void left by others: Such motivations are short-sighted," Yellen said. "The future of our international order, both for peaceful security and economic prosperity, is at stake. This is an order that benefits us all. And let’s be clear, the unified coalition of sanctioning countries will not be indifferent to actions that undermine the sanctions we’ve put in place."

-ABC News' Justin Gomez

President Joe Biden officially announced Wednesday that his administration is "authorizing an additional $800 million in weapons, ammunition, and other security assistance to Ukraine."

Biden made the announcement in a statement released by the White House after he updated Ukrainian President Zelenskyy on the support during a phone call Wednesday morning.

Noting that Russia is preparing to focus its fight in the Donbas region of eastern Ukraine, Biden said the United States would continue to "provide Ukraine with the capabilities to defend itself."

"This new package of assistance will contain many of the highly effective weapons systems we have already provided and new capabilities tailored to the wider assault we expect Russia to launch in eastern Ukraine. These new capabilities include artillery systems, artillery rounds, and armored personnel carriers," Biden said.

He added, "I have also approved the transfer of additional helicopters. In addition, we continue to facilitate the transfer of significant capabilities from our Allies and partners around the world."

-ABC News' Molly Nagle

Jalina Porter, the State Department's deputy spokesperson, is responding to the Russian attack at a Ukraine train station that killed at least 50, saying, "We can no longer be surprised by the Kremlin's repugnant disregard for human life."

Five children were among those killed when Russian rockets struck the station in Kramatorsk in Donetsk Oblast on Friday morning, according to Ukraine's state-owned railway company. At least 100 people were injured, according to Donetsk Oblast Gov. Pavlo Kyrylenko.

Russia has denied involvement in the attack, which occurred as "thousands" of civilians fleeing the Russian invasion were at the train station waiting to be taken to "safer regions of Ukraine," according to Kyrylenko.

"Civilians are killed when they stay in their homes, and they're killed when they try to leave," Porter said. "Actions like these demonstrate why Russia did not belong on the U.N. Human Rights Council, and they also reinforce the U.S. assessment that members of Russian forces are committing war crimes in Ukraine."

Porter declined to say if the department considers the train station attack a war crime, saying, "Assessing individual criminal liability in specific cases is the responsibility of courts, as well as other investigatory bodies. But as the secretary, Secretary [of State Antony] Blinken, has said, 'Those responsible for war crimes and other atrocities committed in Ukraine will be held to account.'"

-ABC News' Conor Finnegan