Mary Decker and Grete Waitz joined about 50 leading women runners from 20 countries in filing a sex discrimination suit yesterday against sports officials for excluding the 5,000- and 10,000-meter events from the 1984 Olympics.

The suit, filed in Los Angeles Superior Court against the International Olympic Committee and the Los Angeles Olympic Organizing Committee, seeks a court order to include the long-distance events for women in the 1984 Summer Games in Los Angeles. A women's marathon and 3,000 meters will be run at the 1984 Games, marking the first time women will be allowed to compete in long-distance events.

"They should have the 10,000 and the 5,000 instead of the 3,000," Waitz said during a press conference in Helsinki. "If women wish to run a longer distance they have to go for the marathon, and there's a very big gap between the 3,000 and the marathon."

Also named in the suit, filed by the American Civil Liberties Union, were the Los Angeles Coliseum Commission, U.S. Olympic Committee, The Athletics Congress, the International Amateur Athletic Federation, Standing and Joint Programs Commission of the IOC, and I. Bechthold, a member of the Women's Committee for the IAAF.