NEW YORK (AP) _ The original ''War of the Worlds'' radio script, including ultimately failed efforts by CBS censors to tone down the realism, fetched $143,000 at auction.

The script, sold at Sotheby's auction house on Wednesday, had sat in writer Howard Koch's file cabinet for years after the 1938 Orson Welles production panicked millions of listeners convinced the world was being invaded by Mars.

''I had a private offer of $60,000. They advised me to take the gamble. I guess it was the right gamble,'' Koch said in a telephone interview from California. Koch adapted the script from H.G. Wells' book for the Mercury Theater.

The 46-page script contains Welles' handwritten changes as well as deletions and alterations by the censors. Welles made numerous changes before air time to smooth the transitions between the music and ''news flashes.''

''I thought it was a pretty good price for six days of work,'' Koch said after an anonymous buyer snapped up the broadcasting relic. ''Of course, I was making $75 a week then for weekly radio shows.''

The broadcast boosted Koch's career. He went to Hollywood, where his screenwriting credits included ''Casablanca'' with Humphrey Bogart, for which he won an Oscar.

''It was resting in my file,'' he said. When friends came to visit, he said, they ''wanted to see the Oscar - they never asked me about this.''

Koch didn't know at first what a stir his realistic script had caused. Tired from around-the-clock work, he went home to sleep during the broadcast. The next morning, he heard people on the street talking about ''invasion'' and ''war.''

''I rushed into a barber shop and said, 'Are we at war?' The barber held up the newspaper headline (about the panic.) It was very strange,'' he said. Afterward, ''They raised me to the magnificent sum of $125'' a week.