Mir is now slated to fight UFC heavyweight champion Junior dos Santos on May 26, 2012, at the MGM Grand Garden Arena in Las Vegas, NV.
White tweeted out the news late Friday night.
Mir's original opponent, Cain Velasquez, will remain on the card, however a replacement opponent has yet to be decided, Velasquez's manager Bob Cook told MMA Fighting's Ariel Helwani.
Overeem's status was thrown into jeopardy earlier this month when the former Strikeforce champion failed a random pre-fight drug test, resulting in a 14:1 testosterone-to-epitestosterone ratio that was well above Nevada's 6:1 limit.
Overeem is currently scheduled to plead his case in front of the Nevada State Athletic Commission on Tuesday. The fighter's manager, Glenn Robinson, recently stated that Overeem had a reasonable explanation for the failed test.
Update: As of Friday night, the UFC has yet to sign an opponent for Velasquez. According to sources, Fabricio Werdum is not being considered for Velasquez. It appears as though they are hoping to move someone else from the 146 card up to fight the former champion Velasquez, however, considering all the moving parts here, nothing is set in stone.
-- Ariel Helwani