Los Angeles, California - Hollywood actors on Wednesday anxiously awaited their union's decision on whether to strike, right at the peak of the film industry's key summer blockbuster season.

The Screen Actors Guild (SAG-AFTRA) has already agreed to one extension of talks with the likes of Netflix and Disney, who have now called in federal mediators to help resolve the deadlock over pay and other conditions.

If the latest deadline of midnight Wednesday passes without a deal, or another prolongation, actors will hit the picket line, joining writers who have already been marching outside studios for more than two months.

A "double strike," not seen in Hollywood since 1960, would bring nearly all US film and television productions to a halt.

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It would also prevent A-listers from promoting some of the year's biggest releases such as Christopher Nolan's Oppenheimer – due to have its US premiere in New York on Monday – just as the industry attempts to rebound from the lean pandemic years.

The massive annual Comic-Con pop culture gathering in San Diego next week could be shorn of its stars, while a scheduled red-carpet launch this weekend at Disneyland for the new Haunted Mansion movie may be stripped back to a "private fan event."

Such is the concern in Hollywood that powerful agency chiefs – who act as gatekeepers to Tinseltown's starriest "talent" – have reached out to SAG leaders, offering to help smooth negotiations.

SAG's 160,000 actors and performers have pre-approved industrial action if a deal is not struck.

While the writers' strike has already dramatically reduced the number of movies and shows in production, an actors' walkout would shutter almost everything.

Some reality TV, animation, and talk shows could continue.

Fox on Tuesday unveiled a fall television schedule full of unscripted series such as Kitchen Nightmares and Lego Masters.

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But popular series set to return to television this year face lengthy delays. And, if strikes continue, future blockbuster films would be postponed too.

Even the Emmy Awards, television's version of the Oscars which is due to take place on September 18, is reportedly mulling a delay to November or even next year.

An actors' strike would mean a boycott of the ceremony by stars.

SAG-AFTRA said Tuesday that it had agreed to the studios' "last-minute request for federal mediation," while voicing skepticism about good-faith efforts on the other side.

"We are not confident that the employers have any intention of bargaining toward an agreement," the union said in a statement.

Should negotiations fail, it will be the first time that all Hollywood actors and writers have been on strike simultaneously since 1960, when actor (and future US president) Ronald Reagan led a showdown that eventually forced major concessions from the studios.

Like the writers, who have already spent 11 weeks on the picket lines, actors are demanding higher pay to counteract inflation, and guarantees for their future livelihoods.

In addition to salaries when they are actively working, actors earn payments called "residuals" every time a film or show they starred in is aired on a network or cable – particularly helpful when performers are between projects.

But today, streamers like Netflix and Disney+ do not disclose viewing figures for their shows, and offer the same paltry flat rate for everything on their platforms, regardless of its popularity.

Muddying the waters further is the issue of artificial intelligence. Both actors and writers want guarantees to regulate its future use, but studios have so far refused to budge.