Texas governor Greg Abbott Thursday criticized President Joe Biden for calling his decision to lift Covid-19 restrictions and masking mandates earlier this week “Neanderthal thinking,” making undocumented immigrants for the persistent Outbreak of the state responsible.

Abbott’s comments come after its much-criticized decision on Tuesday to lift most of the state’s Covid-19 restrictions, including a statewide mask mandate. Texas businesses will be allowed to open “100%” starting March 10, he said. Mississippi Governor Tate Reeves took a similar move around the same time.

Biden on Wednesday hit governors for a “big mistake”, adding that “the last thing we need is Neanderthal thinking”.

Abbott told CNBC’s “Squawk Box” that the comment was “not the kind of word a president should use” and accused immigrants crossing the southern border of spreading the coronavirus. The Republican governor said the Biden government “refused to test them for the virus.”

“The Biden government has released immigrants in South Texas who exposed Texans to Covid. Some of those people were put on buses and took that Covid to other states in the United States,” Abbott told CNBC. “This is a Neanderthal approach to dealing with the Covid situation.”

While the Republican governor failed to provide details, Telemundo reported Tuesday that some migrants released by Border Patrol in the Texas city of Brownsville subsequently tested positive for Covid-19. Since testing began in the city on January 25, 108 migrants have tested positive for Covid-19, which corresponds to 6.3% of all test subjects, according to the report.

“The Biden government must stop importing Covid into our country,” Abbott said.

Senior U.S. health officials have repeatedly urged states not to lift Covid-19 restrictions as statewide coronavirus cases and deaths stall and highly communicable variants threaten to “hijack” the recent decline in infections.

Abbott, however, defended his decision to repeal the state’s mask requirements, claiming that Texans already know that “the safe standard is to wear a mask, among other things.”

“Do you really need the state to tell you what you already know for your personal behavior?” Abbott told CNBC.

The governor added that the state’s coronavirus infections are “at a four-month low” and Texas hospitals stand ready to treat an influx of patients if needed. According to a CNBC analysis of the CNBC analysis compiled by Johns Hopkins University, Texas reports a daily average of around 7,265 new cases over the past week. That’s a decrease from the high of more than 20,400 daily cases the state reported in January.

However, new infections are creeping back across the state, with the average daily new cases increasing nearly 13% from a week ago.

Abbott said most of the state’s coronavirus that spread over the holidays was being driven by indoor gatherings, not restaurants and other businesses. The newly lifted restrictions “aren’t really that transformative” because the state’s mask mandate was not enforced and businesses were already 75% busy, he said.

“Maybe it seems like a big difference to the people in New York,” Abbott said.

– CNBC’s Will Feuer contributed to this report.