LOS ANGELES - TV viewers hooked on cliffhanger episodes of hit shows such as "Heroes" and "Grey's Anatomy" could be left dangling if writers walk off the job.

With Hollywood writers poised to log off their laptops as soon as Thursday, TV networks were bracing for the need to fill the airwaves with reality shows, game shows and even reruns if a threatened strike devours their script inventory.

Viewers could start seeing an onslaught of unscripted entertainment by early next year, when popular series such as "Desperate Housewives" and "Heroes" run out of new episodes.

"I was in a network meeting today, and they were referring to the fact the timing is really good for reality producers," said producer Mark Cronin.

He and partner Cris Abrego have been consistently busy with shows such as "Flavor of Love," "I Love New York" and "The Surreal Life."

But "it's going from 50 mph to 70 mph," Cronin said, adding that networks must "protect themselves and fill their airspace."

Members of the Writers Guild of America and the group representing film and TV producers were set to meet Tuesday with a federal mediator after scant progress in contentious talks that have dragged on since July.

With the current contract set to expire at midnight Wednesday, negotiators remain far apart on the central issue of raising payment for profits on DVDs and shows offered digitally on the Internet, cell phones and other devices.

More than 5,000 members of the Writers Guild of America recently voted, with 90 per cent authorizing negotiators to call the first strike since 1988 if necessary.

"I'm willing to put my family on the line for what's right," said Mick Betancourt, a writer on the show "Law and Order: Special Victims Unit."

Betancourt has a 4-year-old son and a baby due in December but says he is ready to walk a picket line if asked to do so.

The Alliance of Motion Picture and Television Producers, the group that negotiates on behalf of networks and studios, has said networks will continue to air quality programming.

"CBS is not going to go blank," CBS Corp. President and CEO Leslie Moonves has said.

If writers walk out, the effect wouldn't be felt immediately. Networks have enough episodes of shows such as "Ugly Betty" and "CSI" written and in production to last at least through the end of the year and possibly into next February, industry executives and analysts said.

But after that, schedules will run into trouble.

Producers already have tried to hurry shooting in preparation for a strike but not always successfully.

The CBS sitcom "How I Met Your Mother" was asked by 20th Century Fox Television to shoot an extra episode during a planned production break last week.

"It simply would have been impossible, so we said no. That was pretty much where it started and ended," said Jamie Rhonheimer, a writer-producer on the series.

A strike could also leave the hosts of the big Hollywood awards shows speechless.

The Academy Awards, set for February, January's Golden Globes and other shows rely on teams of writers to fashion quips and monologues.

A prolonged writers strike could also affect next year's TV season. Pilots for next fall are being written now and the development process, which includes rewrites and casting, extends through the spring.

"When we stop working, it's going to be a lot of catch-up," to get pilots back on track for the fall, said Patti Carr, a writer who has projects in development with ABC and CBS.

Networks are busy mulling proposed reality projects that aren't governed by guild contracts.

The shows have the advantage of a quick production timeline, said producer Abrego, with a series able to go from "concept to pitch to air" in just a couple months.

Abrego expects to see networks going straight from a pitch to a series order, bypassing the time-consuming production of a pilot.

Viewers like reality shows but may be so angry at interruptions to their favorite prime-time programs that they turn off their sets in disgust, some observers fear.

"You don't want viewers turning away from television, because it can be hard to get them to turn back," said Charles Floyd Johnson, an executive producer on "NCIS."

Advertisers, too, would suffer from a long strike and would make networks share their pain.

Advertisers are "not going to get what they paid for," said analyst Shari Anne Brill of ad buyer Carat USA.

"There will be severe under-delivery (of viewers) on the schedule if you get repeats and less-desirable reality shows," she said. "It puts the networks in a horrific make-good situation."

Ad rates are based on predicted ratings; if a show falls short, networks have to make good the difference with additional commercial time.

She noted that ad revenue already was down from predictions, even before the season began.

In May, when the fall network schedules were introduced, advertisers committed to about $8 billion for prime-time commercials, compared to $9 billion just two years ago.

Film production would not immediately suffer the effects of even a prolonged strike because of the long lead time required to make features.

Still, studios could soon be wrestling with plots and endings for unfinished 2009 blockbusters such as "X-Men Origins: Wolverine" and the next James Bond flick.

Once a film is in production, changes occur almost daily, with writers being asked to create new scenes, punch up dialogue or accommodate an actor's ad-libs or vision for a part.

None of that would happen once writers hit the picket line.

"What they are looking for is a script as close to a locked script as they can find," said Duane Adler, a writer who has been rushing to finish a 2009 movie for 20th Century Fox studios.

It's not a good time for Adler to go on strike, but he is ready to walk out if asked.

"I've got a movie coming out, I've got one I want to direct and one that is being fast-tracked," Adler said. "It's a bad time for me personally. But these things are secondary."