Barr faced questions on Special Counsel Robert Mueller's investigation into possible Russian interference in the 2016 presidential campaign and immigration policy, among others.
Matthew Whitaker was named acting attorney general after Jeff Sessions resigned from the post in 2018. Barr previously served as attorney general under late President George H.W. Bush from 1991 to 1993.
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Fox News' Kaitlyn Schallhorn contributed to this report.