George Kambosos has branded American Devin Haney a "rat" ahead of their fight to become undisputed lightweight boxing world champion.
The pair came face-to-face for the first time in Melbourne before Sunday's showdown, which is expected to draw more than 50,000 spectators to Marvel Stadium.
Kambosos (20-0) owns the IBF, WBA, WBO belts and The Ring magazine strap, while Haney (27-0) has the WBC title.
The victor will emerge as just the seventh undisputed champion of the four-belt era.
It's the Australian's first fight on home soil since 2017, having set himself on the world title path overseas.
Kambosos claimed on Monday that Haney helped him prepare to win his world titles against another American, Teofimo Lopez, in New York last November by sending him messages with details about the Lopez camp.
"This guy is an informant," said Kambosos, who said he still had the messages and could make them public.
"This guy is a rat ... in the Teofimo Lopez fight, against a foreigner, he was messaging me, telling me all the details: 'Teo at the hookah lounge'; 'Teo having problems with his wife'.
"Your own countryman, you were going behind his back, so I'm going to whip your ass and when you get back to Las Vegas, you're going to be on the look out for Teofimo Lopez, because he's going to be looking for you too."
Haney didn't deny he had sent information to Kambosos.
The 23-year-old seemed bemused by the Australian's antics, saying he thought it was an "act".
"When is the act going to stop?" Haney said.
"We can see right through it. Just be you, that's all you got to do - be you. You're acting."
Kambosos replied: "I'd rather be an actor than a rat."
The Sydneysider was set to take on Vasiliy Lomachenko in his first defence, but the Ukrainian pulled out of negotiations in order to defend his homeland against Russia's invasion.
Despite shocking the highly-rated Lopez in a split decision that included him delivering a first-round knockdown, Kambosos is rated the outsider by the bookmakers, who have installed Haney a $1.65 favourite.
Kambosos said that was nothing new.
"That's OK, I've been an underdog my whole career, I was never meant to be here but I've kept turning up," the 28-year-old said.
"I am the top dog, I am the top guy.
"I've had to earn my belts, not like this guy who got given a present. I took the best out.
"That stadium is going to be buzzing with my support. It's a great moment in Australian boxing."
Haney arrived in Melbourne from Las Vegas without either of his trainers - his father Bill, and Ben Davison - who failed to secure travel visas due to historic offences.
He said he wouldn't let the setback stop him becoming undisputed champion and declared he would outclass Kambosos.
"There's nothing that he can do in the ring that is better than me," Haney said.
"I think he's a good fighter but I think I'm on a whole different level."
