Ukrainian President Volodymyr Zelenskyy was meeting with U.S. leaders Thursday in Washington as he seeks more support for his country's fight against a Russian invasion.

Zelenskyy scheduled talks with both Democratic and Republican congressional leaders and Defense Secretary Lloyd Austin at the Pentagon before an afternoon meeting with President Joe Biden at the White House.

The Biden administration has asked Congress to approve $24 billion in military and humanitarian aid for Ukraine.

National Security Council spokesperson John Kirby told reporters Wednesday that the funding, which includes more than $20 billion for defense, would have a 'significant impact on Ukraine's fighting' in coming months.

'It's really important for members of Congress to be able to hear directly from the president about what he's facing in this counteroffensive,' Kirby said, 'and how he's achieving his goals, and what he needs to continue to achieve those goals.'

Additional support for Ukraine has met resistance from some Republican lawmakers, including House Speaker Kevin McCarthy.

'Is Zelenskyy elected to Congress? Is he our president? I don't think I have to commit anything and I think I have questions for him,' McCarthy told reporters Wednesday. 'Where's the accountability on the money we've already spent? What is the plan for victory? I think that's what the American public wants to know.'

Senate Republican Leader Mitch McConnell said Wednesday he would make the case for 'sustained support of the Ukrainian cause, not out of charity, but out of primary focus on America's interests.'

McConnell was critical of Biden, saying he has been too timid in making the case that the United States has 'a fundamental interest in Ukrainian victory and European security.'

Some information for this report came from Agence France-Presse.