Dr. Anthony Fauci and Sen. Rand Paul (R) are taking the gloves off. 

The National Institute of Allergy and Infectious Diseases chief and Kentucky senator verbally sparred during a Senate hearing on Tuesday, after Paul accused the National Institutes of Health of lying about funding controversial research at the Wuhan Institute of Virology. Paul claimed the research could have contributed to the COVID-19 pandemic, The Hill and CNBC report. 

Paul has made such assertions before, but it appears that Fauci is done playing nice. After vehemently discrediting Paul's remarks, Fauci accused the senator of not knowing "what you are talking about, quite frankly, and I want to say that officially. You do not know what you are talking about." Fauci has previously denied that the NIH directly funded the research at the Wuhan lab, per CNBC, and on Tuesday, said the study Paul is referring to does not constitute the controversial gain-of-function research.

After Paul doubled down on his claims, Fauci fired back: "If the point that you are making is that the grant that was funded ... created SARS-CoV-2 ... I totally resent the lie you are now propagating, senator." 

The Kentucky senator countered that he's simply trying to ascertain whether the NIH funded such research, but Fauci criticized the question's underlying implications. "And you are implying that what we did was responsible for the deaths of [individuals], I totally resent that, and if anybody is lying here, senator, it is you."

Watch the full exchange below: