President Corazon Aquino, proclaiming her tenure so far as "a hundred days of freedom," today warned Filipinos not to take newly won liberties for granted and urged self-reliance and sacrifices to overcome persistent economic difficulties.

In a separate statement summarizing the military outlook under the new government, Armed Forces Chief of Staff Gen. Fidel Ramos cautioned that communist rebel influence was spreading and that the situation "may deteriorate seriously if political and economic instabilities persist."

Assessing her first 100 days in office since taking power from president Ferdinand Marcos in a military-led popular revolt, Aquino, in a television address, listed eight areas in which she said freedom had been restored. Among them, she said, were the freeing of the legal system and the economy from abuses by government, freeing the military to "play its proper role as protector of the Filipino people" and giving insurgents an opportunity to live a normal life.

After having captured the imagination of her countrymen and the world by taking power in a "revolution" with a minimum of bloodshed (fewer than 20 persons are believed to have died in the Feb. 22-25 revolt), the inexperienced, 53-year-old Aquino has gone through what normally would be a honeymoon period here under unprecedented, and growing, scrutiny and persistent fault-finding from various quarters at home and abroad.

What Aquino supporters call caution and deliberation have been taken by some critics for indecisiveness, while disgruntled politicians still loyal to Marcos have called her "dictatorial" for not repealing certain Marcos presidential decrees that they now consider "repressive."

Observers say that while Aquino can boast of impressive achievements, problems that bedeviled her predecessor continue to loom large.

Chief among them, are daily fading hopes that large numbers of communist rebels will give up their 17-year struggle against the government now that the "Marcos dictatorship" is gone. The government has failed to put together, or even seriously study, a comprehensive amnesty and rehabilitation program for rebels that would give them a reason for ending their fight.

In interviews with the three major U.S. television networks today, Aquino said her military forces will crack down on rebels if her campaign of reconciliation does not succeed in six months.

In its own assessment of its first 100 days, the New Armed Forces of the Philippines, as the military now calls itself, stated that "on the whole, the insurgency situation has not improved." A statement read by Ramos added, however, that "renewed confidence of the people" in the military had favorably changed the "general situation."

While popularity helps, Ramos' statement at a news conference today made clear that more effort is needed to roll back the communist insurgency. "The situation remains well under control," he said, "but may deteriorate seriously if political and economic instabilities persist. It is urgently vital to generate a greater degree of support and participation of local governments and grass roots institutions in the counterinsurgency and public safety campaign."

The report described Marcos loyalists as a "significant force to reckon with" in maintaining peace and order, but Ramos and other officers later played down the loyalists as any serious military or political threat.

Ramos complained that the reluctance of many mayors and provincial governors appointed by the Aquino government "to boldly come to grips with local security problems" posed a serious difficulty in the countryside.

Giving the military's latest estimate of rebel strength, Ramos said the New People's Army, the armed wing of the Communist Party of the Philippines, now has "about 16,500 regulars, of whom some 11,000 are armed."

He reported that the number of villages affected by the communists' "terroristic and coercive activities" had tripled between 1982 and December 1985. By then the number had reached 7,019, amounting to 17 percent of the 41,615 villages nationwide in 62 out of 74 provinces, Ramos said. By May this year, he said, the number of affected villages had increased by 9 percent to 7,631.

Ramos also reported that insurgency-related violence had increased slightly since the revolution, with an average of 11 persons killed daily during the period compared with 10 a day from Jan. 1 to Feb. 22. He said an average of 14 government troops, insurgents and civilians were killed daily in 1985.

According to a military intelligence report, the number of rebels surrendering nationwide since the overthrow of Marcos comes to a disappointing 1,652, of which only 102 are listed as NPA regulars. The rest include 489 persons described as rebel "activists" and 1,061 members of the communists' "mass base," meaning civilians in rebel-controlled areas. The report said the former rebels had turned in only 73 guns.

In her own generally upbeat assessment of her 100 days, Aquino listed some of her main achievements as freeing more than 500 political prisoners, restoring use of the writ of habeas corpus, freeing the press, dismantling cartels set up by Marcos and his associates and recovering some of their "ill-gotten," hidden wealth.

She also cited cutting the price of oil by 27 percent, repealing "repressive" labor laws, retiring most "overstaying" generals whose tenures had been repeatedly extended beyond mandatory retirement age, setting the country on sounder economic footing and starting the process of drafting a new constitution and holding elections by early next year.

"This has been a hundred days of freedom," Aquino said. But she cautioned that "perhaps the greatest achievement of the first hundred days is also the greatest danger: We are taking freedom for granted."

She added, "It is almost as though a revolution without violence is not to be taken seriously."

Tonight she also said one achievement was that "we are restoring our military to top fighting form," and she credited the armed forces leadership with making great progress in instituting reforms.

Finance Minister Jaime Ongpin said significant economic achievements in the 100 days were an 85 percent increase in foreign exchange reserves to $1.7 billion, a strengthening of the peso exchange rate, reduction of interest rates by about half and obtaining assurances of about $700 million in foreign assistance at a recent donors' meeting in Tokyo.