AIDS is calling the bluff of the health care system.

Increasingly the disease, which has struck more than 136,000 Americans, is highlighting the yawning gaps in medical care for the poor, the chronically ill and the millions of Americans who have only partial health insurance or none at all.

In the process, a kind of medical moralism has provided a backdrop for high-stakes budget decisions, heightening disparities between the so-called "innocent victims" (mostly children) and intravenous drug users and gay men, who are seen by some as having caused their illness by their behavior.

In the competition for AIDS funding, children, who comprise 2 percent of reported AIDS cases, got nearly half -- $14.8 million out of $32 million -- of federal funds appropriated in 1990 for pilot community-based AIDS programs.

At the same time, tens of thousands of inner-city intravenous drug users, often the parents of these children who are also sick with AIDS, threaten to swamp already overwhelmed public hospitals in a dozen or so cities, including New York and Washington.

Public health experts say that AIDS has speeded the creation of a medical underclass among people who are already beset by the problems of homelessness, drug and alcohol addiction and inadequate education.

"AIDS is a metaphor for what's wrong with this country," said June E. Osborn, chairwoman of the National Commission on AIDS. "We're moving quickly to an underclass epidemic. We either have to stare at the underclass and say, 'We don't care,' or we . . . have to do something to change the way health care is administered."

Osborn, dean of the School of Public Health at the University of Michigan, is echoing the conclusions of the chairman of a previous presidential AIDS commission. Two years ago, retired admiral James D. Watkins, now Energy Secretary, decried the federal government's "slow, halting and uneven response" to AIDS, a situation that he said underscored the shaky condition of the health care system.

In New York City, which has been hit hardest by the AIDS epidemic, the problems are especially glaring. "It's like a slowly unfolding national disaster, and people are just now starting to notice," said Timothy Sweeney, an official of the Gay Men's Health Crisis, the nation's oldest and largest AIDS service organization, based in Manhattan. "The AIDS epidemic, {along} with crack and the increasing ranks of the homeless, is overloading emergency rooms. And it's putting us all at risk." The Politics of Funding

Last week, the House of Representatives overwhelmingly passed an AIDS "disaster relief" bill that authorizes $4 billion to be spent over the next five years for outpatient care and community-based programs. The Senate approved a similar bill last month, and the final measure will be hammered out in a conference committee.

Half of the money is to be earmarked for 16 cities, including the District, which have been hit hardest by AIDS. The other half is to be divided among all 50 states; those with more AIDS cases would get more money.

Another measure sponsored by Rep. Henry A. Waxman (D-Calif.) would extend Medicaid coverage for outpatient care and would pay for expensive drugs, such as AZT, for low-income people who are infected with the AIDS virus but have not yet developed the disease. Its aim is to delay the onset of AIDS and to try to prevent unnecessary and expensive hospitalization.

Medicaid, the federal-state program for the poor, is the major source of funding for the care of AIDS patients. But its stringent rules exclude as many as 200,000 who are infected with HIV, according to congressional staff estimates.

"You clearly have a lot of messages being delivered through these bills," said Jean McGuire, executive director of the Washington-based AIDS Action Council, a coalition of community-based AIDS groups that supports the bills. "One is that we've hit a certain critical mass where now everybody knows somebody who has the disease. Another is that we have a flawed {health care} system that is at the root of the problem."

Even so, the fate of the disaster relief bill is uncertain. The Bush administration opposes what it calls "narrow, disease-specific" legislation. Such an approach "sets a dangerous precedent," the White House said in a prepared statement last week.

"Why do it for AIDS and not some other disease?" asked Gail Wilensky, administrator of the Health Care Financing Administration, which manages Medicaid. "The administration is looking at the tougher issue, which is what to do with the uninsured. To the extent that some of the uninsured are persons with AIDS, we will be addressing that." Who Gets the Dollars

Federal spending has steadily increased since 1982, when $8 million was allotted for AIDS. This year, the federal government will spend $2.9 billion on research, care and public health programs, of which $780 million is Medicaid and Medicare funds.

Despite the size of the AIDS budget, federal spending on AIDS is a tiny portion -- about 1 percent -- of the approximately $160 billion the government spends on health.

From the beginning, federal funding favored basic research into the AIDS virus, an enterprise that has enhanced the understanding of other diseases, including cancer, multiple sclerosis and rheumatoid arthritis.

The Public Health Service's Agency for Health Care Policy and Research has estimated that in 1989 about 40 percent of the cost of medical care for AIDS patients was borne by Medicaid and Medicare, another 40 percent was covered by private insurers and 20 percent was paid by individuals or absorbed by hospitals. The cost of caring for people diagnosed with AIDS in 1989 was estimated to be $3.3 billion. Health officials project that 87,000 more people will contract AIDS in 1992 and the cost will double to $6.5 billion.

Part of the problem of determining precisely who pays for AIDS -- which is estimated to cost between $53,500 and $100,580 per case -- is that Medicaid programs vary from state to state and insurance companies do not routinely categorize claims by diseases. In addition, people with AIDS often pay expenses out of their own pockets, fearing discrimination by insurance companies and employers.

In order to better estimate current and future costs, the federal government this fall will launch a study that will review the health expenditures for 2,000 AIDS patients.

Economists say the biggest increase in cost this year is likely to come from wider use of preventive drugs. AZT, the chief AIDS drug, costs $3,000 to $9,000 annually, depending on the frequency with which it is taken. Last March, the Food and Drug Administration announced it would recommend that AZT be prescribed as a preventive measure for those infected with HIV, not just to treat people who already have AIDS.

It is estimated that 600,000 of the approximately 1 million people infected with HIV could qualify for the drug under the new labeling. If they all seek AZT, analysts say the bill could reach $1.62 billion a year.

"AIDS has shown us that we can produce medical miracles for the rich and plain neglect for the poor," said Waxman. Greater Burden on States

Increasingly, the responsibility of paying for AIDS is shifting from the federal government to revenue-strapped states. Those with the greatest numbers of AIDS cases, such as New York and New Jersey, are struggling to find ways to pay.

State programs that cover the cost of AZT vary widely. The District will pay for the drug for those who earn less than $29,900 a year. In Northern Virginia, the annual income limit is $13,461; in Maryland, it is $26,100, and in Texas, it is $11,000.

According to the GAO, many states need help in developing and coordinating health services -- including outpatient care, nursing home care and housing -- for AIDS patients.

Nowhere does the state burden seem as great as in New York, where 28,000 cases of AIDS have been reported so far and an additional 11,000 are expected by the end of this year. The extent of HIV infection is far greater: the state health department estimates between 150,000 and 250,000 are affected. In 1989, about $785 million was spent on AIDS, about 40 percent of which came from state and local sources; this year, the figure is expected to exceed $1 billion.

In New York state, "we are taking care of 14,000 who have HIV infection," said Sweeney. If an early intervention program were started, it is estimated that 120,000 others would qualify.

"The state is not coping now," he said. "It's certainly not going to be able to cope with a much bigger caseload."