After a year of developing the project, Gus Van Sant has bowed out as the director of Warner Bros.’ planned Harvey Milk biopic “The Mayor of Castro Street” due to creative differences over the script.

Van Sant had a vision of the film that differed from Becky Johnston’s recently delivered rewrite and he wanted to pen his own original draft.

After reading an outline by Van Sant, WB brass, Ixtlan producers Oliver Stone and Janet Yang and Storyline producers Craig Zadan and Neil Meron decided to stick to Johnston’s script.

According to Yang, Van Sant told the producers that “he could easily see how someone would want to make this (Johnston’s script), but it wasn’t the movie he was comfortable shooting.”

Based on Randy Shilts’ biography, the story centers on the life and times of openly gay San Francisco supervisor Harvey Milk, who along with the city’s Mayor George Moscone was assassinated in 1978 by former supervisor Dan White.

A WB spokesman confirmed that Van Sant had left the project over “creative differences.” Zadan and Meron, who originally optioned the book and set the project up at WB, declined comment.

Yang said Friday, “We have a tremendous amount of respect for Gus’ work and thought he would be an ideal choice for the project, but when push came to shove and we had the script that we had worked so arduously to arrive at and absolutely believe in, it wasn’t something Gus wanted to direct.”

The producer said that Van Sant — who was unavailable for comment — saw “Mayor” as a smaller, more intimate movie than WB and the producers envision. Yang said, “…. We need a film that can justify the budget we’re talking about.”

Van Sant had been working with Johnston on the script since last year, but was primarily tied up with directing his latest film, Fine Line’s “Even Cowgirls Get the Blues.”

While there was no official start date set for “Mayor,” the producers had hoped to begin lensing the film this summer.

Yang said while discussions are under way about securing an immediate replacement for Van Sant, nobody had yet been approached.

Van Sant’s agent John Burnham, of the William Morris Agency, declined comment on his client’s departure from “Mayor.”

He said the director’s next project will likely be Buck Henry’s screen adaptation of “To Die For,” which Laura Ziskin and Leslie Morgan are producing for Columbia.