LOS ANGELES?Hollywood was counting down the hours to nominations for the Oscars here Monday, with low budget Iraq war drama "The Hurt Locker" aiming to seal its front-runner status in the best picture race.

The Academy of Motion Picture Arts and Sciences will reveal the nominees before hundreds of media packed into the Samuel Goldwyn Theater for the announcement, at 5:38 a.m. local time (1338 GMT Tuesday).

The announcement serves as a starting pistol for weeks of frenzied campaigning by studios bidding to push the claims of their respective films ahead of the Oscars, which take place this year March 7.

All eyes are on the battle for best picture, where "The Hurt Locker" has emerged as the favorite to thwart James Cameron's science fiction blockbuster "Avatar," the most expensive film ever made.

The contrast between the two films couldn't be more stark.

Cameron's film?with a reported budget of $500 million?has rewritten the box office record books, earning more than $2 billion since December to become the highest grossing film in history, ahead of his own "Titanic" (1997).

Yet it is "The Hurt Locker"--directed by Cameron's ex-wife Kathryn Bigelow?which has become a surprise contender after winning a series of important awards regarded as indicators of likely Oscars success.

As a commercial venture, the film has flopped, earning just $16 million worldwide after costing around $15 million.

But Bigelow's gripping story about a US Army bomb disposal squad in Iraq has been a critical darling, picking up numerous awards this year.

The latest of those came on Saturday, when Bigelow piped Cameron to the Directors Guild of America (DGA) Awards top prize?the first time a woman has ever won the award.

In 62 years, only six winners of the DGA award have failed to go on and win the corresponding best director Oscar?and the directing Oscar often goes to the film which wins best picture.

Bigelow's film also scored a surprise win at the Producers Guild of America Awards in January, another reliable Oscars barometer.

"'The Hurt Locker' is definitely the front-runner," said Tom O'Neil, an awards season pundit for the Los Angeles Times's theenvelope.com.

"There doesn't seem to be any confusion. There is a clear consensus within the industry, which is strange because 'The Hurt Locker' is a movie without stars, it's made no money.

"In recessionary times, voters seem to be turning their back on the most successful film ever made in favor of a money loser."

Oscars organizers doubled the number of best picture nominees in a move analysts have said was intended to help boost television ratings for the awards show, which increased by 13 percent in 2009 after hitting a record low in 2008.

The expanded number of nominees could see several interesting sub-plots unfold, with Pixar's "Up" likely to be only the second animated film in Oscars history to win a best picture nomination.

Science-fiction?a genre traditionally ignored at the Oscars?could also be well represented, with "District 9" and "Star Trek" both outside bets to join "Avatar" on the shortlist.

While the best picture race is close, the competition for the coveted acting awards is starting to acquire a look of inevitability.

Popular Hollywood veteran Jeff Bridges is the heavy favorite in the best actor race after already winning a slew of honors for his portrayal of a washed-up country singer in the drama "Crazy Heart."

His likely rivals are expected to include George Clooney for "Up In the Air," Morgan Freeman for "Invictus" and Colin Firth for "A Single Man."

In the best actress stakes, Sandra Bullock has emerged as a front-runner after winning at the Golden Globes and Screen Actors Guild Awards.

Bullock's accolades have come for her performance in "The Blind Side," where she plays a southern housewife who takes in homeless black teen Michael Oher, who goes on to become an American football star.

However, Bullock is expected to face stiff competition from perennial Oscar favorite Meryl Streep, who is tipped to pick up her 16th Academy Award nomination for her performance in "Julie & Julia."

"There's still some suspense about the best actress but it looks like Bullock has the momentum," O'Neil said.

In the supporting acting categories, "Inglourious Basterds" star Christoph Waltz and Mo'Nique of the drama "Precious" are favorites.