BOSTON (AP) _ The National Endowment for the Arts, working under anti-obscenity funding restrictions, denied grants to four performance artists whose acts have strong sexual content.

The four artists, each of whom had received grants in the past, were initially recommended by the endowment's peer panel. Their grants were denied Friday by the NEA's 26-member council and Chairman John Frohnmayer. Fourteen other artists the panel recommended were awarded $104,000.

Frohnmayer, speaking in Portland, Ore., said the federal agency's survival is threatened by a handful of controversial art pieces. Two days earlier in Seattle Frohnmayer said ''political realities'' meant he would likely have to veto some grants recommended by the panel.

''A remarkable experiment that has lasted the last 25 years and has so enriched our country is indeed threatened ... because of 20 images out of a million we have funded,'' Frohnmayer told the City Club in Portland.

The NEA's 1990 appropriations bill included anti-obscenity restrictions adopted amid protests over works such as Robert Mapplethorpe's homoerotic photography and Andres Serrano's crucifix submerged in urine - both of which received federal funds.

Friday's decision prompted charges the artists were the latest victims in a movement to clamp down on artistic freedom.

''I'm outraged,'' said John Fleck, a Los Angeles-based performance artist whose pieces touch on such topics as AIDS, religion, the environment and homosexuality.

''I think there's a strong movement going on to wipe out different voices, to have a homogeneous voice that suits certain people's morals,'' Fleck said.

Last year Fleck received an NEA grant, but his application was rejected Friday along with those of artists Tim Miller, Holly Hughes and Karen Finley.

''We feel basically that it's like the wall is going down in Berlin while it's coming up here in the United States,'' said Michael Overn, who is Finley's husband and manager.

Philip Arnoult, director of the Theater Project in Baltimore, said distorted descriptions of the artists' work in the media had done ''terrible damage'' to the performers themselves.

''These are fellowships for artists who are making a significant contribution to the field in the solo performance world,'' said Arnoult, who was chairman of the panel on theater. ''And some of them are dealing with issues of sexual identity, of oppression in society, of the plague of AIDS.''

In recent weeks such venerable arts groups as the New York and Oregon Shakespeare festivals, the University of Iowa Press and the Paris and Gettysburg reviews have returned their 1991 NEA grants to protest the federal anti-obscenity guidelines.