Conor McGregor -- Takes $10 Million Hit ... UFC Officially Calls Off Fight

Conor McGregor's Facebook statement wasn't enough to move the UFC -- the organization is officially calling off his fight with Nate Diaz ... a fight that came with a $10 MILLION paycheck, TMZ Sports has learned.

Our sources tell us ... besides the massive payday, the UFC told Conor it was willing to move mountains to accommodate the fighter during the UFC 200 media tour.

Not only did UFC offer to fly Conor to every destination on a top-of-the-line private jet ... but also offered to ship out every single piece of his gym equipment from Iceland to Vegas for this weekend's media event so there wouldn't be a kink in Conor's training.

We're told McGregor was told his gym would be set up identically to his Iceland training center and it would all be ready to go the second he stepped off the plane.

Still, McGregor refused to budge -- and our sources tell us Conor was "shocked" when he was told the media obligations in Vegas were mandatory.

As for Conor's future ... we're told he blinked on retirement partially because of anti-doping rules that require fighters to wait 4 months after they un-retire before they can fight again -- and Conor doesn't want to wait that long.

Dana White told Colin Cowherd he believes McGregor will fight for the UFC in the next year -- but our sources tell us it will NOT be against Nate Diaz. Instead, he'll have to fight Frankie Edgar or Jose Aldo.