Soprano Beverly Sills, who will begin her new career as director of the New York City Opera on July 1, announced some of her plans for the company at a press conference yesterday, including a fund-raising drive.

"I am shooting for a $12-million fund," she said in New York. "This will be banked and the revenue used for specific purposes.

"I already have a half-million dollars in a gift from a very generous anonymous friend who came to this country from Europe and made a lot of money here," she said. "He has given me this sum to be used at my discretion, but for American artists."

Sills also announced a competition for a new, one-act opera, between 30 and 50 minutes in length, to be given its premiere in the 1980 season. The prize is $10,000, and the competition is open to all American composers.

Revenues already in hand, Sills said, will be used for rehearsals. "I do not want any of our conductors to conduct a performance without a full rehearsal. Nor will a major artist be asked to go onstage without a full stage rehearsal.

Sills also said she plans "to keep my complement of artists 95 percent American. However, if any of you has a young Pavarotti or Domingo up your sleeve, I will give you my telephone number."

She said, "We are sedulously avoiding conflicts with the Metropolitan's repertoire. I have had conversations with James Levine [the music director] and Joan Ingpen [in charge of scheduling] about repertoire plans, and except for certain bread-and-butter items such as "Boheme," "Butterfly" and "Traviata," we will not be doing operas the Met is doing. We will be doing "Freischuetz," which the Met does, but they are not doing it in the seasons we are.

"Here comes a problem," Sills continued, "about 'Juana La Loca,'" That is the new opera by Gian Carlo Menotti, commissioned for Sills by the late Larry Deutsch of Los Angeles, an opera fan and Sills enthusiast. It is to have its world premiere in San Diego on May 30 with Sills in the title role.

"I was hesitant about it," Sills explained. "I come in as director and then I sing.But the score says 'For Beverly Sills on her 50th birthday,' and it was Larry Deutsch's wish that I should sing it, so we are going to honor his wish, and I will also sing it here. It will be the San Diego production, staged by Tito Capobianco, with John Mauceri conducting.

"Another very important part of my five-year plan concerns young singers," she said. "I have heard some that are very exciting, some very young and green. But I can see growth under normal circumstances, so that in three to five years, they will be ready for certain operas."