CEBU CITY, Philippines (AP) _ Corazon Aquino called on the Philippine armed forces Sunday to support the rebellion led by two high-ranking defense officials, and said President Ferdinand E. Marcos should resign immediately.

Mrs. Aquino, who claims Marcos used fraud and terrorism to rob her of victory in the Feb. 7 special election, canceled a planned anti-Marcos rally in the southern city of Davao to return to Manila to follow developments in the defection of Defense Minister Juan Ponce Enrile and deputy armed forces chief Lt. Gen. Fidel V. Ramos.

Both men holed up in military camps outside Manila, which Marcos said Sunday had been surrounded by armed forces units loyal to him.

At a news conference in Cebu, Mrs. Aquino said, ''For the sake of the Filipino people, I ask Mr. Marcos to step down now so that we can have a peaceful transition of government.''

She appealed to ''decent elements'' of the Philippine military to back Ramos and Enrile.

''These two gentlemen have made it very clear that they are out to support the people's will and not to be loyal to any one person,'' she said.

Referring to a statement issued by the White House on the latest developments in the Philippines, Mrs. Aquino said she had read it and was ''very happy'' with its contents.

The White House statement, issued Saturday, noted the actions of Enrile and Ramos and said their allegations of election fraud ''strongly reinforce our concerns that the recent election were marred by fraud, perpetrated overwhelmingly by the ruling party'' of Marcos.

Asked if she didn't feel Reagan should be calling for Marcos to step down, Mrs. Aquino said, ''Well, I'm doing that for him.''

Mrs. Aquino said she did not see an American hand in events. ''I just see people power and Filipino people power really now manifesting itself,'' she said.

She called for civilians to join soldiers guarding Enrile and Ramos to show their support, as hundreds have already done, and said she might eventually visit the camps.

Mrs. Aquino said she was not calling for revolution in the Philippines but for a continuation of peaceful protest. She has supported nationwide anti- Marcos strikes, school walkouts and boycotts to protest Marcos' inauguration on Tuesday.

Mrs. Aquino cut the news conference in Cebu City short after about 10 minutes, saying, ''The earlier I get back to Manila, the better.''