Prajin told ESPN.com on Saturday he has had "multiple conversations" with UFC officials regarding the potential bout. On Friday, Justino's former co-manager and wrestling coach Tito Ortiz told "Inside MMA" the UFC had already officially "offered" the fight to Justino, setting off a wave of speculation.
While Prajin refused to discuss any details regarding negotiations, he did confirm they have taken place and that Justino (14-1) is confident she can make 135 pounds by December.
"I don't negotiate in the media, nor do I disclose negotiations to the press," Prajin said. "What I can say, and the only reason I say this is because of what is going on between Tito and Dana -- I can confirm that I had multiple conversations with the UFC in the last week regarding Cris and a potential fight [against Rousey] in December.
"I can also confirm the end result of those conversations is that Cris is agreeable to fighting Ronda on Dec. 5 at Cowboys Stadium [at 135 pounds]."
UFC president Dana White told Yahoo! Sports on Saturday that Ortiz's claims of a fight offer were "completely untrue."
"The problem is, this kind of thing gets out there and picks up momentum when there is no truth to it. And it was just something that [Ortiz] decided to make up. But it's not true," White told Yahoo! Sports.
The UFC declined further comment on the situation to ESPN.com.
A potential fight between Rousey (12-0) and Justino has been in the making for years. Justino, 30, is the current Invicta FC featherweight champion and former Strikeforce champion. Rousey is the current UFC bantamweight champion. Rousey started her career at featherweight, but dropped to the 135-pound division in March 2012.
The biggest obstacle to making the fight thus far has been weight. Rousey has established herself as a mainstream star as the UFC's bantamweight champion. The UFC currently does not promote a female featherweight division, due to lack of depth. UFC CEO Lorenzo Fertitta has stated numerous times the UFC would not book a fight between Rousey and Justino above 135 pounds -- and that Justino would have to prove she can make the 135-pound limit before fighting Rousey.
Justino has long expressed doubt about whether or not she could make the weight, but Prajin says the addition of nutritionist George Lockhart has changed the entire camp's stance on the matter. Prior to an Invicta featherweight title defense in July, Justino weighed in at 144.6 pounds and could have been significantly lighter, Prajin said.
Earlier on Saturday, Justino wrote on social media she would be willing to fight Rousey in April, if the UFC champion was "busy" in December. The UFC has publicly stated Rousey's next title defense would be in December, but against Miesha Tate, whom she has beaten twice.
Justino also mentioned Olympic-style drug testing ahead of a potential fight against Rousey, who has repeatedly accused her of performance-enhancing drug use. Justino was suspended for one year in December 2011 after testing positive for an anabolic steroid. She has passed multiple random drug tests since. Should Justino book a UFC fight, she would be subject to the company's anti-doping policy, which is implemented by the United States Anti-Doping Agency and includes blood and urine tests.