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

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

Russia is staging helicopters, artillery systems and troops in preparation for what is expected to be a renewed offensive in the Donbas region of eastern Ukraine, a senior U.S. defense official said Wednesday.

Russian forces have been using the cities of Belgorod and Valuyki in Russia near Ukraine's northeast border as primary sites to stage equipment and resupply troops, the official said. The United States is now seeing a third Russian town, Rovenki, also near the Ukraine northeast border, being used for that purpose.

The official said there's already signs that Russian forces are on the move south to the Donbas region.

"We continue to see units flowing into the northern Luhansk Oblast, that north part of the Donbas," the official said. "They're flowing in from Valuyki and from that town called Rovenki."

The long Russian convoy is heading south and, at last check, was near the city of Izium in eastern Ukraine, according to the official.

Other Russian troops to the south of Izium appear to be working to improve their mobility and firepower in the region, the official said.

"We've seen them try to erect a temporary bridge over a local river," the official said. "They're increasing their artillery in the area."

-ABC News' Matt Seyler

In a brief moment of joy amidst the brutality of war, rescuers in eastern Ukraine on Wednesday pulled a puppy alive from the rubble of a bombed building, authorities said.

The rescue unfolded in Mykhailivka in the Donetsk region, according to the Donetsk Regional Police.

Police released a video showing rescuers digging through the rubble with bare hands to reach the trapped pooch. Rescuers said they heard the puppy whining as they were picking through the rubble.

"Thanks to the boys for doing everything quickly and promptly here," said the dog’s owner while holding the trembling puppy in his arms

Finland and Sweden -- both traditionally militarily neutral countries -- are considering a dramatic pivot in their security policy following Russia's invasion of Ukraine.

Leaders of both countries publicly stated during a joint press conference Wednesday that they are considering taking steps to join the NATO alliance.

"The European security architecture has changed fundamentally after Russia's invasion of Ukraine," Finland's Prime Minister Sanna Marin said. "The change in the security landscape makes it necessary to analyze how we best secure peace for Finland and in our region in the future."

Swedish Prime Minister Magdalena Andersson added, "We have to really think through what is best for Sweden and our security and our peace in this new situation and, of course, what is happening and the discussion in Finland is important for us to follow. Therefore, we need to have a very close contact, but we have to have a process in Sweden to think this through."

Last week, NATO Secretary-General Jens Stoltenberg said he's had close contact with political leaders of both countries and has conveyed that it's up to them whether to decide joining NATO.

"But if they apply, I expect that 30 allies will welcome them and that we will find ways to also address the concerns they may have about this interim period between (when) they have applied and until the last ratifications has taken place," Stoltenberg said.

Kremlin spokesperson Dmitry Peskov warned that further expansion of NATO to include Finland and Sweden will not contribute to security in Europe.

"In itself, the alliance is rather a tool sharpened for confrontation, this is not an alliance that ensures peace and stability," Peskov said, according to Russian state-run news agency TASS.

-ABC News' Christine Theodorou