Russia-Ukraine updates: 2 US veterans who joined Ukrainian forces missing

U.S. Secretary of State Antony Blinken has authorized the Pentagon to provide $800 million in new military aid to Ukraine that the White House announced earlier Wednesday.

Blinken said that though Ukrainian forces are "regaining ground," the war is "far from over," with Russia repositioning itself for renewed attacks in eastern and southern Ukraine.

"The United States, its Allies and partners must take action now to surge additional military assistance as Ukraine prepares for the next phase in the fight for its freedom and its very future," Blinken said in a statement.

The new package includes increased capabilities, such as sea drones, armored vehicles and long-range artillery, he said.

-ABC News' Conor Finnegan

The U.S. will be moving "as quickly as possible" to get the latest military aid announced Wednesday into Ukraine, Pentagon spokesman John Kirby said.

"We will literally start right away," Kirby told reporters during a briefing Wednesday.

"We're aware of the clock. And we know time is not our friend," he continued.

The weapons systems, which include 155 mm howitzer artillery, are intended to help Ukraine fight against Russia in the eastern Donbas region and met requests that came from the Ukrainians, Kirby said.

"We tailored this list specifically to meet the needs that they have asked for, with respect to what's going on in eastern Ukraine," said Kirby. "That's what's really driving this."

-ABC News' Luis Martinez

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.