The comments from Barr, who was Trump's attorney general from February 2019 through December 2020, were made at a time when many other prominent Republicans have been hesitant to criticize Trump
Calling it a "joke of an indictment," Trump told the audience in Georgia the prosecution would further bolster his support within the party.
Trump is due to make a first court appearance in the case in a Miami court on Tuesday, a day before his 77th birthday.
The criminal case, brought by the US Department of Justice, amounts to another legal setback for Trump as he seeks to regain the US presidency next year.
A court document identified the accused as linked to Hezbollah and their ally, the Amal movement.
Maya Benvenisti wore a bikini to the Western Wall to protest against a law that would punish women for dressing immodestly at the Kotel.
The suspect was an external contractor whose job it was to protect the women he allegedly sexually abused.
The soldier and three other soldiers reportedly attempted to hide the assault from their commanders.
Rioter established a Snapchat group chat to organize participation in riots throughout Jerusalem.
The victims, women aged 15-21, were immigrants from the former Soviet Union and in financially unstable situations.