Update3: Barr says that the Justice Department's Inspector General is working on reviewing the process used by the FBI to obtain a FISA surveillance warrant on Trump campaign aide Carter Page, and that the IG report will be complete in May or June. Barr also said that he's overseeing a separate wider investigation.
Bill Barr says Mueller was offered an opportunity to review the "no collusion" letter issued on March 24, and declined. Stands to reason, therefore, that Mueller had full faith in Barr to represent his findings accurately.— Michael Tracey (@mtracey) April 9, 2019
He also said he will testify before the Judiciary Committees about all aspects of the Mueller report upon its release, including working with Rep. Nadler to explain the redactions.