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

White House national security advisor Jake Sullivan hinted Thursday of more sanctions coming against Russia in the "next week or two" aimed at targeting ways Moscow is evading sanctions already imposed.

“Where our focus will be over the course of the coming days is on evasion,” Sullivan said Thursday at the Economic Club of Washington. “As Russia tries to adjust to the fact that it’s under this massive economic pressure, what steps do they take to try to evade our sanctions and how do we crack down on that? And I think we'll have some announcements in the next week or two that identify targets that are trying to facilitate that evasion both inside Russia and beyond."

When Sullivan was asked whether sanctions will automatically be lifted if a negotiated peace deal between Russia and Ukraine is worked out, he appeared cautious with his words, saying, “a lot of that depends on what the shape and scope” of the agreement is.

“A lot of it depends on what the Ukrainians, in consultation with us and the Europeans come to agree to," Sullivan said. "You know, we're not going to do a deal over the head of the Ukrainians where we give a bunch of sanctions relief to Russia. But if some measure of sanctions relief were built in to some credible diplomatic solution led by the Ukrainians, that's something that we would happily discuss."

But Sullivan said Russian oligarchs shouldn't expect to ever get back their yachts and other assets seized under sanctions that have been imposed, saying the ultimate goal is "not to give them back” once the war is over.

“The president is actively looking at how we can deal with the fact that as we seize these assets, our goal is not to give them back. Our goal is to put them to a better use than that," Sullivan said. "But I'll be careful in what I say today because there's an ongoing kind of policy process around how we end up dealing with that question. But, rest assured, that the goal is not just to sit on them for a while."

-ABC News' Justin Gomez