Luke Bryan, Lionel Richie & Charlie Puth in the mix for new 'American Idol' judges' panel

ABC's American Idol judging panel is beginning to come into focus.

With Katy Perry already set, sources tell The Hollywood Reporter that ABC, producers FremantleMedia and Core Media are narrowing the field to Lionel Richie, Luke Bryan and Charlie Puth to join Perry on the judges' panel. ABC, Fremantle and Core all declined comment.

Sources note that while all three names are rumored to be in the mix, negotiations with anyone have yet to begin. Richie is considered to be likely as he remains an internal favorite among all three parties; Bryan would make sense given ABC's relationship with country music -- the Disney-owned network is the home to the Country Music Awards, among others; and singer Puth is seen as less likely of the trio.

See photos of the original "American Idol" judges' panel:

The remaining judges' slots need to fill up fast. Auditions are scheduled to start Aug. 17, in Florida, and thus far only Katy Perry is onboard. It was just one week ago that American Idol finally locked down Ryan Seacrest to return as host, a negotiation that stretched to nearly three months despite the fact that it was considered a foregone conclusion.

What judges will fill the vacancies aren't expected to have near the star wattage of Perry, who took a significant chunk of the budget with her reported $25 million contract. ABC and Fremantle are said to have talked about ways to prevent the show from suffering the price problem it had toward the end of its original Fox run, when skyrocketing talent salaries caused the show to lose money.

See photos of Ryan Seacrest through the years: