The most recent coup attempt against the Aquino government of the Philippines and military losses to communist guerrillas there have grabbed the attention of official Washington and touched off demands for new U.S. initiatives. But what to do, in view of the sensitive nature of the problems and severe cutbacks in foreign-aid funds, is an open question in the Reagan administration.

Officials of the State and Defense departments have devoted many hours to analyzing the Philippine situation since the Aug. 27 coup attempt raised concerns about the government of President Corazon Aquino, especially its military-related problems. So far, according to officials involved in the internal discussions, nobody has come up with a plan of U.S. action.

"These are some of the most sensitive issues of domestic policy in the Philippines," said a senior State Department official, citing personnel changes and policy shifts in the Philippine presidential palace and in the Philippine military establishment. "If we had a lot of resources available, perhaps we could pour them in" and be in a better position to give advice, but there is no immediate prospect of that, the official said.

The situation is especially delicate because those under strongest criticism in Manila for alleged ineffectiveness -- including presidential aides Joker Arroyo and Theodore Locsin Jr. and the armed forces chief of staff, Gen. Fidel V. Ramos -- have been closest to Aquino since she took power in Febuary 1986. Moreover, questions of civil-military authority and the related issues of policy toward the communist-led insurgency are among the touchiest in Manila.

In recent days, U.S. policy was to state strong support for Aquino and strong opposition to the coup attempt, and to express the hope that she will deal vigorously with formidable problems that confront her. The unstated implication was that she has been less than vigorous in some of her responses.

A handicap in the current Washington-Manila communications process is that the new U.S. ambassador, Nicholas Platt, presented his credentials only days before the coup attempt and has not had time to build a personal relationship of confidence with Aquino or others in the Manila power structure.

Platt, a Foreign Service veteran with extensive Asian experience, was nominated by President Reagan last April. Rather than being sent quickly because of the dangers in Manila, Platt's confirmation was delayed for almost two months by Sen. Jesse Helms (R-N.C.) and confirmed only in early August.

A major asset is that Aquino and her Philippine democracy have unusually broad support across the U.S. political spectrum. This has been so since the dramatic events of early last year, which engaged Republicans and Democrats alike and captivated much of the U.S. public. Since then, foreign-policy experts of the right and left have been energized by their perceptions of the threats in Manila.

For U.S. conservatives, the threat of the communist New People's Army has become even more serious for a country where the United States has major military facilities and security interests, and the Philippine government's ineffectiveness in dealing with the insurgency has become even more dangerous.

The conservative Heritage Foundation last week declared in a report that, despite the recent coup attempt, "it is not the Philippine military but the communists who pose the greatest threat to Aquino and Philippine democracy." The recommendations of the report, by policy analyst Richard D. Fisher Jr., are to double U.S. military aid, provide more intelligence information and urge Aquino to develop a coordinated civil-military counterinsurgency plan.

The Heritage Foundation report parallels a pessimistic report on the status of the Philippine armed forces in July by retired general Richard G. Stilwell, who was a senior Pentagon policy-maker earlier in the Reagan administration and who reflects the views of some active U.S. military and intelligence officials. "The armed forces of the Philippines are not now capable of coping with the counterinsurgency tasks they confront," wrote Stilwell, who recently returned from a trip to Manila.

U.S. liberals and others with a stake in Aquino's brand of democracy have become alarmed about a different threat: the repeated coup attempts by forces loyal to former president Ferdinand E. Marcos and now an even more serious coup attempt by dissident military "reformists."

For the 1986 Asian "triumph for democracy" to be toppled by an undemocratic military coup would be a bitter pill for those who backed Aquino and would be a major setback for the U.S. self-image and foreign policy.

On this point, the newly organized Council on U.S.-Philippine Relations, a national support group modeled to some degree on the pro-Israel American Israel Public Affairs Committee (AIPAC), said in a statement drafted for its introductory news conference later this week that "The Philippines represents what American foreign policy in a dangerous world should be all about. If we fail to do whatever we can to help make Philippine democracy flourish, our nation will have lost whatever claim to the ideals of freedom and democracy that we still hold dear."

The new council, headed by Roger J. Fish, a former Peace Corps volunteer in the Philippines and a D.C. public schools official, is recommending a near-doubling of U.S. economic aid to the Philippines and a small increase in U.S. military aid.

In view of the draconian cuts recently voted on Capitol Hill in foreign aid for fiscal 1988, which begins Oct. 1, the chances for substantially increased assistance to the Philippines seem far from high, despite the serious situation there, the major U.S. interests at stake and the broad U.S. political support.

"Subject to the constraints of the budget process, we are at a point when the administration and Congress will try to go out of their way to be helpful to the Philippines," said Under Secretary of State for Security Assistance Edward J. Derwinski. "But we can't rob Peter to pay Paul by taking hundreds of millions in new money for the Philippines from other countries which are already suffering drastic cuts."

After Aquino received fervent cheers from a joint session of Congress last September, the lawmakers -- in an extraordinary gesture -- voted an extra $200 million in aid to the Philippines, roughly doubling the 1987 aid program to a total of $406 million. In recent months, however, the administration and friends of the Philippines in Congress have had to battle vigorously to make good on these sums in the face of cutbacks in appropriations.