WATCH: White House press secretary Jen Psaki holds news briefing

White House press secretary Jen Psaki defended the U.S. position delivering aircraft to a besieged Ukraine.

Watch Psaki’s remarks in the player above.

She told reporters on Thursday that U.S. intelligence and military experts assessed adding aircraft to Ukraine was “not likely to significantly change the effectiveness of the Ukrainian Air Force relative to Russian capabilities.”

The White House has faced Republican criticism that it isn’t providing enough weapons or intelligence to Ukrainian President Volodymyr Zelenskyy. The Biden administration is currently opposed to a Polish plan to donate old Russian-made warplanes to Ukraine, out of concern that Putin may view that as an escalation by the U.S. or NATO.

Top U.S. intelligence officials admitted Thursday that they underestimated Ukraine’s ability to defend itself against Russia’s invasion, a mistake for intelligence agencies that have otherwise been lauded for accurately predicting Russian President Vladimir Putin’s intention to launch a war.

Psaki also said the Biden administration had determined the best way to provide support for the more than 2 million refugees was to coordinate with countries bordering Ukraine.

The U.S. House passed a massive spending bill overnight that includes $13.6 billion in aid for Ukraine and its European allies.

The legislation includes $6.8 billion to care for refugees and other economic aid to allies.

Polish President Andrzej Duda warned of a “refugee disaster” if Poland doesn’t receive more assistance to help house and feed Ukrainians fleeing the conflict. He said he asked visiting U.S. President Kamala Harris for the U.S. to “speed up” the process for those Ukrainian refugees who would want to go to the U.S. and might have family there.