"We called to say Michelle and I couldn't be prouder to endorse you and to do everything we can to get you through this election and into the Oval Office," Obama told Harris.
In a statement announcing their arrests, Attorney General Merrick Garland described the cartel as "one of the most violent and powerful drug trafficking organizations in the world."
Friday's ceremony marked the 25th anniversary of the conflict's end, when sustained diplomatic pressure from Washington and elsewhere forced Pakistan's withdrawal.