McGregor, who surged through the featherweight ranks before knocking out champion Jose Aldo in 13 seconds in December, has become the UFC's hottest property with his outrageous trash-talking outside the cage and vicious skills inside it.
While there has been speculation Jon Jones could step into the main event at UFC 200 to fight for the light heavyweight title, the former champion's laboured win over Ovince Saint Preux on Sunday may have prompted White to give his most bankable asset another chance.
Diaz has said he would only fight McGregor and that he would take a vacation rather than fight a replacement.
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"Happy to announce that I am BACK on UFC 200!" McGregor said on his Twitter account, thanking White and UFC CEO Lorenzo Fertitta for "getting this one done for the fans".
The brash Irish fighter, who says he has made $400 million for the organisation, has been training in Iceland for the fight with Diaz, who choked him into submission in a welterweight non-title bout in March.
McGregor had at one point suggested he was retiring from the sport of mixed martial arts but later said the promotional work was distracting him from training.
(Reporting by Peter Rutherford; Editing by John O'Brien)
