The New People's Army, the Communist guerrilla organization that has been waging an insurgency in the Philippines for 17 years, is willing to negotiate a cease-fire with newly installed President Corazon Aquino but will not surrender its arms, according to a source close to the Communist Party.

"The position of the party is to support Cory [Aquino] but not to give all-out allegiance," said the source, who has authoritatively stated Communist Party positions in the past. "The party will be supportive of her positions that are in line with nationalist democracy," he said in an interview.

"The NPA [New People's Army] will agree to a negotiated cease-fire but must have some concessions," the source said. He did not specify what these conditions might be but said categorically that the guerrillas "would not lay down their arms."

In the past, one of the key demands by the Communists has been an immediate abrogation of the agreement on the two U.S. military bases in the Philippines. Aquino has said she would allow the bases to stay until the agreement expires in 1991, but has said she would keep her options open after that.

The stance of the party, which controls the New People's Army, comes in response to Aquino's call for a six-month cease-fire with the rebels. She repeated the appeal, which she advanced during an election campaign for the presidency, in her first news conference yesterday since taking over as undisputed president Tuesday following the departure of the deposed leader Ferdinand Marcos.

While the Communists are prepared to support the popular Aquino and negotiate with her, potential problems appear to exist over several issues. One complaint that already has surfaced concerns the composition of her Cabinet, announced yesterday. "You don't see the interests of the basic masses being represented in her Cabinet," said a leftist leader. "There are no workers or peasants, just the same ruling class." He was particularly critical of the presence of four former members of Marcos' ruling party and two other ministers who, he said, "represent big business." A potentially bigger problem, analysts said, is Aquino's insistence that the insurgents give up their weapons and renounce violence as conditions for a general amnesty. In a policy speech she made Jan. 23 while campaigning against Marcos, Aquino said that such an amnesty "will be granted to all political detainees and all political offenders who forswear the use of violence against the state." Before granting an amnesty, she said, she would seek a six-month cease-fire to "enable my government to take steps, immediately upon assumption of office, to redress the legitimate grievances of those who resorted to armed struggle."

She warned that "I will use the power of the state to fight any force, whether Communist or not, which will seek to overthrow our democratic government or destroy our cultural heritage, including our belief in God. But I will respect a Communist's right, or anybody's right for that matter, peacefully to sell his ideas to others."

In the same speech, Aquino estimated the number of guerrillas at 16,000.

She has said repeatedly that many are not Communists but alienated young people driven to the hills by Marcos.

A staff report to the U.S. Senate Select Committee on Intelligence in November 1985 put rebel strength at about 30,000 regulars and part-time irregulars. It said the Communist Party, with at least 30,000 members, "controls or is contesting control of settlements inhabited by at least 10 million people" in this archipelago of 55 million inhabitants.

The Reagan administration also sees the insurgency, which grew dramatically under the 20-year Marcos administration, as one of the toughest problems facing Aquino's new government.

Military and leftist sources agree, however, that Aquino is in a strong position in relation to the Communist Party of the Philippines and its leftist allies because of the unexpected, swift success of the military mutiny, and the largely middle-class popular revolt supporting it, that swept her to power.

The mutiny and the massive street demonstrations stripped Marcos of support and forced him to flee Malacanang, the presidential palace, Tuesday.

Aquino was transformed overnight from a "defeated" presidential candidate, a victim of large-scale electoral fraud, to a triumphant, popularly installed president.

"My feeling is that the NPA is back to square one," said a western military attache. "Their mass base will be stripped away, and a lot of their soldiers will be stripped away. The reason they joined the NPA is gone."

Whether or not that happens, it is clear that the pro-Aquino revolt took the Communists and their allies by surprise. Some leaders of leftist political organizations acknowledge that it was a setback, leaving them out in the cold to ponder what they now concede was a mistake in boycotting the Feb. 7 presidential election. For it was the election, fraud-ridden as it was, that set the stage for the sudden three-day revolt, and the boycotters never had time to jump on the bandwagon.

According to an official of a leading leftist coalition known as Bayan, the left had wanted to "seize the initiative" during the revolt and capture town halls and other government installations in the provinces to stake a claim to participation in a post-Marcos government.

"But events unfolded too quickly, and we lost the initiative," the official said. "Now we can't even demand a share in political power." Instead, the group, which U.S. officials have labeled a Communist front, plans to "continue to organize the basic masses" and take up a watchdog role to promote its causes.

One of the causes currently at issue is the release of political prisoners. While 39 were ordered freed today from military detention centers, leading Communists remained in jail, and leftist leaders charged that the military was blocking their release.

Aquino said in her news conference yesterday that she wanted to study at length with Defense Minister Juan Ponce Enrile the issues of legalizing the Communist Party and dealing with the insurgency. Enrile, one of the leaders of the military mutiny, served in Marcos' Cabinet for 20 years and played a key role in administering martial law from 1972 to 1981.

Indeed, it is particularly galling to the Communists and their allies that longtime Marcos allies in the government and military are now wearing a "revolutionary" mantle. Besides Enrile, they include Armed Forces Chief of Staff Gen. Fidel Ramos and senior officers who joined his call to arms against the Marcos government Saturday.

"If you look at their records, they [Enrile and Ramos] have their crimes also," said Lorenzo Tanada III, a student representative on the Bayan national council. "The Bayan position is that justice should be done to representatives of the dictatorship whether they turned at the beginning or at the end."

The most controversial of the newly appointed officers is Maj. Gen. Prospero Olivas, named by Ramos yesterday as acting chief of the Philippine Constabulary and Integrated National Police.

Olivas, a latecomer to the mutiny, was among 25 military men and one civilian tried for the August 1983 assassination of opposition leader Benigno Aquino Jr., the new president's husband. All the defendants were acquitted in what Corazon Aquino and other opposition figures called a travesty of justice.

Enrile was "an accomplice" in the killing, torture and detention of Marcos opponents for years, the source said, "and to my mind he must stand trial."