"The rumor is true," White said via Twitter. "Carlos did accept the fight today."
Condit defeated Diaz by unanimous decision Saturday night at UFC 143 in Las Vegas. He used solid footwork and head movement to elude Diaz's pressure attack, while delivering counter-strikes to impress the judges.
After the scores were read, Diaz expressed disappointment with the judges' scorecards (48-47, 49-46 and 49-46) by vowing never to compete in mixed martial arts again.
"I'm not going to accept the fact that this was a loss," Diaz said. "I pushed him back the whole fight. I took him down. I think I'm done with this MMA. It's been a good time.
"I don't need this. I pushed this guy the whole fight. I landed the harder punches. He kicked me a few times."
Diaz (26-8, one no contest) wasn't the only fighter disappointed by the outcome.
Current UFC 170-pound titleholder Georges St. Pierre expressed his desire to fight Diaz and wanted him to come away victorious. St. Pierre was slated to face the Diaz-Condit winner in a unification bout later this year.
Diaz, the former Strikeforce welterweight champion, has been verbally taunting St. Pierre for months. The two were scheduled to meet in Saturday night's main event, but St. Pierre suffered a torn ACL in his right knee in December and pulled out of the fight.
St. Pierre expects to resume full training in July. He has targeted November for his return to action.
Condit (28-5) was originally scheduled to fight St. Pierre, but agreed to step aside for Diaz. That goodwill gesture did not prevent fans from criticizing Condit after the fight at Mandalay Bay Events Center.
Many mixed martial arts fans expressed their disagreement with the result, booing Condit during his postfight interview inside the Octagon.
UFC has not yet set a date or location for the Condit-Diaz rematch.
Franklin McNeil covers mixed martial arts and boxing for ESPN.com. Follow him on Twitter at www.twitter.com/Franklin_McNeil.