Hollywood producers and writers reached a tentative agreement Wednesday to end a crippling 150-day strike by the Writers Guild of America, one of the longest in film industry history.

The breakthrough came in an all-night bargaining session engineered by entertainment lawyer Kenneth Ziffren. The 15 hours of talks resolved a seemingly intractable dispute over residuals to writers for programs sold overseas, which had blocked repeated settlement efforts.

Negotiators for the two sides announced the agreement at about 4:45 p.m. in the company of a federal mediator. The guild's board approved the deal in a 25-to-6 vote with one abstention, and scheduled membership ratification votes Sunday in Los Angeles and New York.

The Los Angeles meeting is set for 11 a.m. at the Hollywood Palladium. The strike against more than 200 movie and television producers, including all the major studios and networks, could end as early as Monday if the pact is approved.

The paralyzing walkout forced layoffs at many studios and brought financial hardship on thousands of other workers. The economic casualties ranged from production personnel whose shows were sidelined to restaurants with heavy industry trade to typing services used by screenwriters.

The networks have pushed back the debut of the new television season to October or later, and production on some motion pictures has been delayed.

Brian Walton, chief guild negotiator, said the contract was "enormously" better than one producers offered just before the strike began March 7, and "significantly" better than a June 16 offer that was overwhelmingly rejected by union members. At a press conference, Walton said he expects members to feel "some disappointment" with the deal following their long strike. But in a telephone conversation immediately afterward, he said: "There were a lot of human reasons in the negotiators' decision (to settle). . . . The time was right to make a deal."

In a crucial point in the agreement, writers agreed to a new formula for calculating payments, called residuals, they receive when reruns of one-hour television programs are sold for syndication in the United States. The new formula, based on a percentage of sales, reflects a decline in the syndication market for one-hour shows. But in exchange, the writers won the right at some future point in the four-year contract to submit to binding arbitration a request for a return to the existing fixed-payment residual formula if the syndication market improves.

Under the current system, the writer's residual for a one-hour show is about $16,000. Under the new system, it could be as low as half that for a show with weak syndication sales, or 50% more for a hit.

Right to Choose

On residuals for shows sold to foreign countries, an expanding market, writers won the right to choose during the contract life between the current system, which pays a maximum of about $4,400 for a one-hour show, or a new formula that would pay 1.2% of the producers' foreign sales of a program, as long as that is not less than 85% of the current residual, or more than 130% of that figure.

According to Walton, the agreement also calls for increases in minimum pay of 5% in the first 18 months, 5% in the next 18 months and 4.5% in the fourth year of the contract. It also includes provisions making it easier for writers to reacquire scripts if a studio does not actually produce them, and the guild's first agreement covering shows produced for basic cable services such as the Arts & Entertainment and USA networks.

Under a letter of settlement attached to the contract, the guild will drop an anti-trust suit filed against the studios and networks during the strike. Walton said the producers in recent bargaining dropped a previous demand that the guild provide amnesty to any writer who violated strike rules by working for studios during the walkout.

In announcing the settlement at a brief press conference, J. Nicholas Counter III, chief negotiator for the Alliance of Motion Picture and Television Producers, avoided any claim of victory. "No one wins a strike," said Counter.

Given past support for union leaders, it appeared likely that members would approve the contract.

"If the leadership is recommending acceptance, I'm confident that I will go along with it. People are tired of being out," said writer-producer Robert Eisele ("The Equalizer"), considered among the most vocal supporters during the strike.

Although the guild membership mostly showed impressive support for leaders throughout the strike, there was some intense discord. A small corps of dissident writers threatened to break away and return to work as early as this week. The long walkout also strained relations between the writers guild and the Directors Guild of America, as each union accused the other of making conflicting claims upon the production companies.

As the strike wore on, about 150 smaller production companies--including those that produce NBC's "The Tonight Show" and "The Cosby Show"--signed interim contracts with the guild. But no major alliance company broke ranks, dashing union hopes that the producers could be split.

Instead, major studios announced that they would produce programs with non-union writers, scripts written overseas and by reshooting old scripts with news actors. For example, ABC said it would revive the television program "Mission Impossible" by filming the shows in Australia using teleplays written when the show was first aired in the 1960s and 1970s. The networks also asserted they could fill air time with more news programs, which were unaffected by the strike, and shows that needed no scripts, such as variety program.

It was unclear Wednesday whether the studios and networks would proceed with any of these plans.