A union representing 13,000 nurses at nine Southern California hospitals announced that they intend to strike June 10 if they do not reach agreement with hospital officials on their contracts. The strike would include nurses from all University of California hospitals, Citrus Valley Medical Center in Covina, San Pedro Peninsula Hospital, and Olympia Medical Center in Los Angeles, said Jill Furillo, a nurse and bargaining director for National Nurses United, which includes the California Nurses Assn. union. Furillo said contract negotiations stalled because of hospital officials' unwillingness to adhere to state-mandated nurse staffing ratios, particularly during nurses' meals and breaks.