Tony Bellew and David Haye have held "positive talks" over a rematch, says trainer David Coldwell.
Bellew, who defeated Haye at the O2 in March, has resumed negotiations with the former WBA heavyweight champion as the rivals attempt to organise a rematch.
However, despite early negotiations going well, Coldwell told Sky Sports that it is not guaranteed that both parties will agree terms for a second matchup.
He said: "All I know is that obviously there are talks going on.
"They have been back and forth for quite a while now really I suppose, but I believe there are positive talks going on.
"It is one of those fights that are possible. Whether or not it gets finalised or not, I'll believe it when I see it."
Coldwell also confirmed that Bellew has other options for his next bout if an agreement with Haye can't be reached, with the Scouse fighter highlighting Andre Ward or Joseph Parker as potential opponents.
"There are other options, but we're just seeing which one is the best one really," Coldwell added. "Best and most viable, that's what you've got to look at."
The 34-year-old's trainer also noted that they were looking at a December date for the fight, which would correspond with Haye's expected return from injury.
Haye is on course to return to the ring before the end of the year, as he continues to recover from the Achilles problem which hampered him in his first encounter with Bellew.
Although the 34-year-old is expecting to return to action before the end of the year, he claimed that he is less optimistic of securing rematch with the man who beat him in March.
"The plan is [to return] before the end of the year," Haye said. "That's what I've said since I had my operation. That's what I believe will happen.
"[A rematch with Bellew] might happen but only if we can get on the same page. We have always been on different pages. I won't be holding my breath for that one.
"If it's supposed to happen it will happen but at the moment I wouldn't put money on it."
The Press Association contributed to this report