United Farm Workers leader Cesar Chavez, who has gone without food 33 days, will break his protest fast on Sunday at a Catholic Mass at the union's headquarters, a spokeswoman said today.

Delores Huerta, UFW vice president, said Chavez, 61, made the decision Wednesday night to end his water-only protest on the 36th day.She said Chavez will attend an 11 a.m. Mass at the union's 40-acre headquarters and then "break bread."

The labor leader has been fasting since July 17 to protest pesticide dangers to farmworkers and to support the union's 4-year-old table grape boycott.

Dr. Fidel Huerta, who has examined Chavez daily since he began the fast, said Wednesday he did not know if Chavez could maintain the fast until Sunday.