To have one trade union paralyse Hollywood was strange; two doing it in quick succession feels like carelessness. A threatened walkout by actors, which could begin as early as next week, is throwing major film and television studios into chaos.

The contract dispute, this time between the Screen Actors Guild (SAG) and their white-collar bosses, the Alliance of Motion Picture and Television Producers (AMPTP), is causing what industry experts have called a "virtual strike".

Production deadlines for dozens of major projects have been scrapped amid growing signs that the SAG, which has 120,000 members, will fail to resolve its dispute before a deadline for industrial action on Tuesday next week.

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Most major film shoots are now either being put on hold, or wrapping-up early to avoid disruption.

"No one is doing anything that finishes after 30 June, and nobody's starting anything now," one lawyer representing actors told The Hollywood Reporter. "This is the impact of a strike already."

Victims of the crisis include Sir Ridley Scott, who has delayed filming his Robin Hood remake, Nottingham, until late summer. Martin Scorsese, Peter Jackson and Steven Soderbergh are meanwhile rushing to finish their current projects by 1 July. Those films are Shutter Island, starring Leonardo DiCaprio, The Lovely Bones and The Informant.

Other stars who are likely to have a busy week include Will Ferrell (currently working on Land of the Lost), together with Seth Rogen (Observe and Report), and the James Bond actor Daniel Craig.

The entire cast of High School Musical 3; GI Joe; When in Rome and Disney's Race to Witch Mountain are also racing to complete shoots before any picket lines appear.

At issue in the SAG dispute are almost 70 elements of a proposed new contract with the major studios that is being haggled over at AMPTP's headquarters in Sherman Oaks, Los Angeles. Bones of contention are said to include payments for film and video clips screened online, the issue that was at the heart of the previous writers' dispute.

With no resolution on the horizon, several major projects are planning to suspend actual filming and work on special effects for however long it takes to resolve the dispute. The Transformers sequel is about to begin a planned hiatus, along with Angels & Demons, the follow up to The DaVinci Code.

On television, the autumn season for dozens of network shows, which was already knocked out of schedule by the 100-day writers' crisis, now faces renewed chaos. The hit show Gossip Girl is in the middle of filming its second series. Army Wives, Saving Grace, The Closer and Monk are also mid-production, while 24 has decided not to chance its arm and cancelled an entire year of shows.

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Whatever happens, the "summer of discontent" could not have come at a worse time for an industry that is counting the cost of its first strike in 20 years.

The Milken Institute, a Californian economic think- tank, recently estimated that the state would already lose about $2.1bn (£1.07bn) in output as well as 37,000 jobs by the end of the year.

"Even if the actors strike doesn't happen, there is already an economic impact going on which is currently affecting production schedules," said the study's author, Kevin Klowden. "Even a smaller strike would slow down the recovery."

The dispute has gained added importance in trade union circles because SAG's smaller rival union Aftra recently concluded contract negotiations with the AMPTP. In a Monty-Python style dispute, SAG is now attempting to prevent Aftra's members endorsing that deal.

"We're frustrated and discouraged that the talks have stalled because SAG's Hollywood leadership is focused on its campaign to interfere with the affair of a fellow union," said AMPTP's spokesman, Jesse Hiestand, yesterday. "The producers remain committed to avoiding another harmful, unnecessary strike and to reaching another fair and forward-looking labour agreement."

Whatever happens, those worst hit by any disruption will be actors and technical staff. The Actors Fund, a charity that assists film-industry employees who have fallen on hard times, said yesterday that it has received 800 requests for support already this year, more than four times its usual level.

"Usually we give out $250-$350,000 a year in emergency financial assistance in Los Angeles," said a spokesman. "This year, we've already given out $1.2m. If this new strike happens, it will be devastating for people."

George Clooney recently donated $25,000 to the Actors Fund, but other major stars are actively lobbying to prevent the strike. Tom Hanks recently took a full-page advert out in Variety urging both sides in the dispute to mend their differences, while T R Knight, the star of Grey's Anatomy (another show that begins filming this week) told a recent interviewer: "I support my union, but I'm hopeful that it's going to resolve this because it's not time for another strike."

The turmoil may also spill over into the political arena. California's Governor, Arnold Schwarzenegger – who is a SAG member – was the subject of a heated editorial in yesterday's Los Angeles Times criticising his failure to intervene in the dispute. "We saw how you handled the writers' strike... It was, frankly, kind of a girlie- man performance," it read.