SAN FRANCISCO (AP) _ Forty million people in the United States cannot read above fourth-grade level, experts said Friday as they asked newspaper editors to join the fight against illiteracy.

''We have really given ourselves a whole new group of people who are in slavery,'' said Arthur R. Colby, chairman of Literacy Volunteers of America.

About 27.5 million of those who can't read or write above fourth-grade level are Americans born in this country, Colby told about 900 members of the American Society of Newspaper Editors at their annual convention.

''It's a scary, scary thing to even imagine in your mind where you would be if you didn't know how to read or write,'' said Bob Tettleton, a former illiterate who is now warehouse foreman for the Contra Costa Times and a director of Literacy Volunteers.

''You have the best vehicle there is to generate enthusiasm in the community,'' said Tettleton, noting that he was encouraged to get help after seeing a Times article about a 60-year-old in a reading program.

Tettleton said his inability to read had isolated him as an adolescent, leading him into trouble and eventually prison. Half the inmates in the country, Colby said, can't read.

Arthur White, chairman of Jobs for the Future and board member of Reading is Fundamental, said literacy programs have been set up at 3,300 sites around the country, but added, ''I think we're losing, rather than gaining, on this problem.''

He urged editors to support a campaign to bring attention to the problem, encourage illiterates to seek help and to promote literacy programs.

Alfred B. Bennett, literacy specialist for the California State Library, said close to 40 states have a public program to fight illiteracy, but he agreed with Colby that more help is needed from the private sector.

''As newspapers get the word around about how serious this issue is, I believe we can win this important battle,'' he told the editors.