The British comedian Sacha Baron Cohen, best known for his characters Borat and Ali G, has become one of the first victims of a looming strike by Hollywood film actors.

Last week Steven Spielberg shelved plans to shoot The Trial of the Chicago Seven, in which the 36-year-old Londoner was to have played a 1960s antiwar protester alongside Will Smith and Philip Seymour Hoffman. The director does not think he can complete the film before his cast is asked by union leaders to go on strike this summer.

An actors’ strike would be the second walkout to close the film and television business this year. Writers have only just returned to work after their three-month strike. They won a share of internet broadcast profits and actors want that included in contracts due to be signed by July 1, plus a share of other profits.

Spielberg’s decision will disappoint Baron Cohen, who, according to Hollywood reports, has been struggling to finish writing Bruno, a comedy about a camp Austrian fashion reporter he originally devised for Da Ali G Show on Channel 4.

Baron Cohen, whose girlfriend Isla Fisher is also an actor, wants to be taken seriously in Hollywood. He would have played Abbie Hoffman, a self-styled anarchist who stood trial after a hippie protest at the 1968 Democratic party convention in Chicago ended in street battles with the police.

Hoffman mocked the trial, in which the defendants became known as the Chicago Seven. Despite appeals by Norman Mailer, the novelist, and Jesse Jackson, then a budding politician, he was jailed for five years. The convictions were overturned on appeal, but Hoffman, who suffered from drug and mental problems, remained a countercultural icon until his suicide in 1989.

Will Smith has said he would “make the time” to play the role of Bobby Seale, a leader of the Black Panthers civil rights organisation, but it is not clear whether even Spielberg will be able to reassemble the cast after a strike.

Spielberg is the first director to suspend production, but many other Hollywood films will be in jeopardy unless a last-minute deal is struck. An actors’ strike could hit cinemas by Christmas.

Michael Bay, director of last summer’s hit Transformers, said he was keeping his fingers crossed for a peace deal as he prepared to start filming a sequel. “If there is a strike, we close down,” he said.

Paul Schiff, who produced the Julia Roberts film Mona Lisa Smile, said he had had to “surrender” and cancel three films due to start shooting this spring. “We could not be sure we could finish in time,” he said.

The writers’ strike cost the industry £1.5 billion, and studios are still scrambling to fill holes in the television schedules. Some British broadcasters that depend on US imports may have to use more repeats.

An actors’ strike would threaten the Star Trek and Terminator sequels due for release next year. Actors have been pressing the Screen Actors Guild (SAG) to speed up negotiations.

Screen Actors Guild official website

Video: footage from the SAG awards 2008

Times Recommends

• Thousands of Tamils dying in 'welfare camp'
• Jackson 'rebuilt his nose before he died'
• Renewed Iran protests crushed by militia