WATCH: White House press secretary Karine Jean-Pierre speaks on U.S. aid to Ukraine

The U.S. announced it will send an additional $1 billion in military aid to Ukraine, as America and its allies provide longer-range weapons they say can make a difference in a fight where Ukrainian forces are outnumbered and outgunned by their Russian invaders.

Watch the briefing in the player above.

President Joe Biden and his top national security leaders said Wednesday the U.S. is moving as fast as possible to get critical weapons to the fight, even as Ukrainian officials protest that they need more, faster, in order to survive.

Speaking to reporters at the White House briefing, John Kirby, the National Security Council coordinator for strategic communications, told reporters Biden spoke with Ukrainian President Volodymr Zelenskyy earlier in the day to confirm the additional assistance.

“That brings the total amount of security assistance that we provided to Ukraine to approximately $5.6 billion just since Russia launched its assault in late February and then approximately 6.3 billion since the beginning of the Biden-Harris administration,” Kirby said.

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Asked about reports that Kremlin critic Alexei Navalny was transferred to a higher security prison facility, Kirby said he can’t “absolutely confirm” the reports.

But he said the administration continues “to reiterate our demand for his immediate and unconditional release from from being imprisoned over spurious charges after a sham trial.”

Kirby also told reporters he can’t confirm reports that two U.S. veterans from Alabama who were in Ukraine assisting in the war against Russia have gone missing.

But he said if it’s true, the White House will do everything it can “to get them safely back home,” and urged Americans not to go to Ukraine to fight.

“If you feel passionate about supporting Ukraine, there are any number of other ways to do that that are safer and just as effective,” Kirby said.

Kirby defended President Joe Biden’s upcoming trip to Saudi Arabia which will include talks with Crown Prince Mohammed bin Salman, who U.S. intelligence officials have determined ordered the 2018 killing of U.S.-based journalist Jamal Khashoggi, saying human rights and press freedom “mean a lot to President Biden.”

“He’s not going to be bashful about raising those issues with any foreign leader,” Kirby insisted.