The UFC still has the 185-pound contest officially listed on its website for the UFC 284 event, which is scheduled to take place on Feb. 11 in Perth, Australia, but efforts have fallen through to finalize the bout.
Costa (14-2) referred to the fight announcement as "fake news" on his social media platforms and told Submission Radio in a recent interview that he and the UFC were in discussions on a potential new contract.
"UFC tried everything in their power to get [Costa] to the fight ... The Perth fight is not happening," Whittaker said Monday in a video posted to his Instagram account. "They're looking to reschedule me [in] March, April. This is very upsetting. I'm sorry to all the friends, fans and family heading over there to watch me work. It's out of my hands."
The UFC has not announced a new plan for Whittaker, a former champion who fights out of Australia, however sources say it's currently likely he will be moved to a later date.
According to sources, Costa and the UFC have discussed a new contract, but nothing has been agreed upon. It's unclear if and when those talks will resume. Costa, 31, has repeatedly said in interviews and on social media he is on the final fight of his deal.
Costa commented on an Instagram post that the UFC "should stop being petty," and added that fights are falling through due to the promotion's "lack of negotiating skills."
The UFC 284 pay-per-view is the highest anticipated event on the promotion's currently released schedule, as it will feature a champion vs. champion fight between lightweight title holder Islam Makhachev and featherweight and pound-for-pound king Alexander Volkanovski. Yair Rodriguez and Josh Emmett will also meet for an interim featherweight title.