MMA: Israel Adesanya v Robert Whittaker confirmed for UFC 243 in October

Israel Adesanya's highly anticipated middleweight title unification bout with Robert Whittaker is finally official.

The trans-Tasman showdown will headline UFC 243 on Sunday October 6 in Australia at a city that's yet to be determined.

Initially that location was rumoured to be either Sydney or Brisbane, but the clash with the NRL Grand Final on the same day has seen Melbourne emerge as the more likely host.

Both fighters were present for the announcement at a UFC press conference held in Las Vegas on Saturday (NZT) where they exchanged some light barbs, before standing for the first of many square-offs.

In April, 'The Last Stylebender' beat Kelvin Gastelum in a five-round war to claim the interim middleweight belt while champion Whittaker recovered from hernia surgery.

Injury and illness have meant the NZ-born Aussie has only fought twice in the past two years, a period of inactivity Adesanya - one of the busiest fighters in the promotion-  was quick to highlight.

"The last 18 months have been crazy," Adesanya said. "Six fights in and I'm the champ. I can't say that for him.

"The last four months, I took some time off and relaxed. Went on holiday. he keeps talking sh*t about me the whole time and I've just been chilling, minding my own business.

"I'm motivated, I'm inspired and I'm ready to go."

Whittaker acknowledged the unique threat Adesnanya posed following such a lengthy layoff, but was baffled by the suggestion he'd been bad mouthing his opponent.

"It's going to be a very difficult challenge," said the 28-year-old." He's got a very dangerous skillset.

"I don't believe I've been talking that much sh*t. I don't know what I did to him to upset him."

Support at the T-Mobile Arena appeared evenly split between the two as they took to the stage to face-off, Adesanya hoisting his belt high after a prolonged staredown.

UFC president Dana White was adamant the bout will be held in a stadium rather than an arena, with Melbourne's Docklands Stadium and Sydney's Bankwest Stadium mooted as two potential options.