White House press secretary Jen Psaki on Thursday defended President Biden calling the decision of two GOP governors to lift mask mandates as "Neanderthal thinking" after some conservatives took offense to the criticism.

"I think the president, what everybody saw yesterday, was a reflection of his frustration and exasperation, which I think many American people have, that for a almost a year now people across the country have sacrificed, at many times they haven’t had information they need from the federal government," Psaki told reporters at a briefing.

"They haven’t had access to a greater understanding of what the public health guidelines should look like, and those include many many people in Mississippi and Texas, in Ohio, Florida, in every state across the country," she added.

Psaki said Biden was likening the decisions to lift mask mandates and allow most businesses to operate at full capacity to the behavior of a Neanderthal, and was not singling out any individuals. She added that Biden would continue to work with governors of both parties on the pandemic response.

Biden on Wednesday expressed disappointment with the decision of Republican governors in Texas and Mississippi to lift mask mandates in their states, which undercuts a push from the White House for Americans to mask up for the first 100 days of the new administration.

"We are on the cusp of being able to fundamentally change the nature of this disease because of the way in which we're able to get vaccines in people's arms," Biden said. "We've been able to move that all the way up to the end of May to have enough for every American to get — every adult American to get a shot. And the last thing — the last thing we need is Neanderthal thinking that, in the meantime, everything is fine, take off your mask."

The comments prompted blowback from some conservatives who took issue with Biden's choice of words.

"Mississippians don’t need handlers. As numbers drop, they can assess their choices and listen to experts. I guess I just think we should trust Americans, not insult them," Mississippi Gov. Tate Reeve (R) tweeted.

Sen. Marsha Blackburn (R-Tenn.) suggested on Fox Business that the reference to Neanderthals was actually a term of endearment because "they are resilient, they're resourceful, they tend to their own."

And Kayleigh McEnany, who served as press secretary in the Trump White House, linked Biden's comments to those of Hillary Clinton when she said in 2016 that half of Trump's supporters could be placed in a "basket of deplorables."

Mississippi and Texas this week lifted their mask mandates and other coronavirus restrictions, citing declining case numbers and hospitalizations. But health experts have warned that doing so could reverse progress in the fight against the pandemic, particularly with the spread of more contagious variants.