President Corazon Aquino today appealed again to Communist rebels to stop fighting and negotiate, but warned that a "reformed and reinvigorated" armed forces would pursue those failing to answer her call for national reconciliation.

Speaking at graduation exercises at the Philippine Military Academy, she also said, "We must purge our armed forces of all that has dishonored them in recent years," an apparent reference to abuses by the military under deposed president Ferdinand Marcos.

A recurrent theme in the speech was that, with rare exceptions, the 250,000-man armed forces were still on moral probation and had many sins to be forgiven and much to learn about democratic practices.

"Past abuses will be investigated and any officers and men guilty of crime or serious misconduct will be dealt with appropriately," Aquino said. "Only through an honest explanation of the past can a clean start be made for the future."

The speech was particularly important for the Aquino government, whose future depends on the stability of the unusual military-civilian coalition that brought her to power. While the speech appeared to be an attempt to reassure the military that Aquino plans to build it into a strong and modern force, it also made clear that the new president intends to call the shots on policy and the issue of military accountability. Addressing herself to Communist insurgents, she said, "now that evil has fled from the land" with Marcos' ouster, she would "soon" ask guerrillas of the New People's Army "to rejoin your people in rebuilding our country. There should be no more reason to continue fighting." She did not spell out exactly what she had in mind. But she apparently was hinting that a long rumored partial amnesty proposal was in the offing to lend further credence to her election campaign pledge of a cease-fire to promote peace talks with the 16,000-man New People's Army, the armed branch of the Philippine Communist Party.

Arguing that the Marcos government "turned its back on reconciliation and had become, through goons, warlords and cronies, the most effective recruiter of the New People's Army," she stated, "I will not have this again."

Since Aquino took office Feb. 25, the Communists have rejected her key condition that they first surrender their arms. Fighting has continued unabated in many parts of the country.

The continued fighting reportedly has been a source of tension between Aquino and her civilian advisers on one side and the military men who supported the rebellion against Marcos on the other. Defense Minister Juan Ponce Enrile, for example, said last week that the government should press the Communists to show quickly that they plan to agree to a cease-fire.

Only two days after Aquino became president, the Army commander in central Luzon ordered new search-and-destroy operations in that key sector, which lies north of Manila and near Subic Naval Base and Clark Air Base, the largest American military facilities outside the United States.

Although the president said it "was too early to claim" how many Communist fighters "will heed our call and return to us," she warned that anyone "undermining the stability of the country must understand they will not be facing the demoralized forces of Marcos."

"Rather," she said, "they will be facing a national Army, trained and ready to protect our sovereignty and the democratic government chosen by the people." She added, "let nobody mistake the importance we attach to building a strong and disciplined armed forces."

Balancing her encouragement for Defense Minister Enrile and Gen. Fidel Ramos, the armed forces chief of staff in charge of the "new" Philippine Army, were repeated references to the military's failings under Marcos.

His 20-year reign, she said, "did you more harm than you even now may recognize."

She pointedly recalled that "this revolution" that put her in power "began with a bullet shot by a soldier into the head of my husband," Benigno Aquino Jr. He was killed at Manila airport as he stepped from an airliner returning him from American exile on Aug. 21, 1983.

Four days ago she appointed a Human Rights Commission to investigate abuses, and its military member has warned that no official -- not even Enrile or Ramos -- would escape its scrutiny.

Dressed in a yellow suit, the color she has made her political emblem, the president returned time and again to her favorite theme, that the armed forces must respect democratic practice and "civilian supremacy over the military."

And, as she twice warned, democracy meant that the military should "stay out of politics."

Praising the academy staff and cadets, who sided with the successful rebellion against Marcos loyalists, she argued, "Your actions were not a revolt against, but a restoration of, legitimate government."

For those who still doubted her ability to deal with the military in this largely male supremacist society, she said, "Let me be clear about one thing: I mean to fulfill my responsibility as commander-in-chief." Ramos and the rest of the military hierarchy "will report directly to me" and "neither errors of policy nor gross misconduct will long escape my attention and rebuke.