(Reuters) - Hollywood's awards season reaches its climax at Sunday's Oscars, with a cliffhanger over the top prize after a season marked by dark horses, renewed anguish over diversity, and a South Korean underdog that could snatch victory from the biggest names in show business.

While dark comic book movie "Joker" goes into the ceremony with a leading 11 nominations, it's the immersive World War One movie "1917" that has emerged as the film to beat in the best picture race after winning a slew of accolades in the last five weeks.

Yet a win for "1917" is far from a foregone conclusion, with South Korean social satire "Parasite" and sentimental favorite "Once Upon a Time in Hollywood" from Quentin Tarantino also jostling for attention from the 8,000 voters of the Academy of Motion Picture Arts and Sciences.

"Right now, it's looking like '1917''s to lose," said Alison Willmore, film critic at pop culture website Vulture. "I can see a world where 'Parasite' could be a dark horse candidate. It's so beloved. Once we get past that, there is probably a chance for 'Once Upon a Time in Hollywood'," she said.

Korean-language film "Parasite" seems certain to take the renamed best international feature Oscar and would make history if the black comedy about haves and have-nots in modern Seoul also takes home the best picture statuette.

Martin Scorsese's mob saga "The Irishman" seems to have lost momentum despite lavish early praise and a cast that includes Robert De Niro, Al Pacino and Joe Pesci. But it has failed to take home major acting or directing awards this season, likely dashing Netflix's best hope so far of picking up its first best picture Oscar.

The best director category, a controversially all-male affair, is equally hard to call according to Oscar pundits, with a lineup featuring Sam Mendes ("1917"), Scorsese, Todd Phillips ("Joker"), Tarantino and Bong Joon Ho ("Parasite").

Owen Gleiberman, chief film critic at Variety, said he could see the Academy Award going to any of the five directors. But he added; "I feel like it could be Quentin's year because he has said he's only going to make 10 films. This is his ninth.

Sure bet for Brad?

Some races appear to be already locked up. Brad Pitt has never won an acting award, but he has charmed awards audiences with his witty speeches and supporting actor performance as a laid-back stunt double in "Once Upon a Time in Hollywood."

"Like Clark Gable, he (Pitt) has an aura, just an effortless zen, macho thing," said Gleiberman.

Joaquin Phoenix has dominated best actor prizes for his terrifying portrayal of an isolated loner in "Joker," while Renee Zellweger seems to have locked up best actress for playing an aging Judy Garland in "Judy."

"She's playing beloved Hollywood royalty," said Scott Feinberg, awards columnist for The Hollywood Reporter. A win by Zellweger would defeat "Harriet" star Cynthia Erivo, the only person of color in the acting lineup that has renewed the #OscarsSoWhite furor despite four years of efforts to diversify the academy's membership.

Taking place without a host for the second year, Oscar organizers have given few details of the ceremony, other than to announce live performances by original song contenders Elton John, Idina Menzel, Randy Newman, Chrissie Metz and Erivo.

Five-time Grammy winner Billie Eilish will also take the stage for what is billed as a special performance that could see her debut her theme song for the upcoming James Bond movie "No Time to Die."

The Academy Awards ceremony takes place on Sunday in Hollywood and will be broadcast live on ABC television, starting at 5 p.m. PT/8 p.m. ET (0100 on Monday GMT). (Reuters)