WASHINGTON (AP) _ Veterans organizations say they will oppose Reagan administration proposals to charge veterans more money when they buy a home with a VA loan.

Veterans groups also voiced concern that the fiscal 1988 budget President Reagan proposed Monday would scale back VA medical care, with small cuts in employee ranks and numbers of patients treated.

''If they propose that, we'll meet them in the halls of Congress,'' said Cooper Holt, executive director of the Veterans of Foreign Wars in Washington. ''I still happen to think we have more friends over there than they do.''

The administration's budget resurrects a proposal rejected by Congress in the past to raise the fee paid by veterans obtaining a VA guaranteed home loan from 1 percent to 2.5 percent of the amount of the mortgage.

For the VA medical system, the budget proposal would mean a loss of 3,810 jobs - to about 190,000.

The president's budget proposes total outlays for the VA of $27 billion in fiscal 1988, up from the $26.7 billion in fiscal 1987.

But the administration also proposed a cut of $75 million in the amount Congress has already agreed to spend on VA health care in the current 1987 fiscal year that began Oct. 1.

The budget proposal would save $31 million by cutting payments to veterans' survivors. Holt said the move would eliminate a $150 allowance for a burial plot for 85 percent of veterans - all except those with service-related disabilities or VA pensions.

American Legion spokesman John Hanson said his organization of former servicemen considers the loan fee increase ''just unacceptable to us.''

VA spokeswoman Donna St. John said no decision had been made on what hospitals would see staff cuts, but that physicians probably would be included.

''It means there just will be less care available,'' said Dr. Paul W. Schafer, a surgeon and executive director of the National Association of VA Physicians. ''This is just another step to do away with the veterans medical care program.''

The budget proposal estimated a decrease in the number of people receiving in-patient treatment at VA hospitals, nursing homes and other facilities of 11,583, to 1.4 million, in 1988. The number of out-patient visits would decline by 113,000, to 20.4 million.

Schafer said that while the proposal would increase VA spending, it is not a big enough increase to cover inflation in medical costs.

Disabled American Veterans spokesman Jerry Atchison said, ''Even though the budget of the VA is going up, ... it's obviously still not enough.'' He said the number of patients would decline at a time when the VA is turning away 250,000 veterans a year who seek VA medical care.

Rep. G.V. ''Sonny'' Montgomery, D-Miss., chairman of the House Veterans Affairs Committee, said through a spokesman that Congress was unlikely to approve the rescission or the home-loan fee increase.

By law, the VA provides free medical care to all veterans disabled due to their military service and to former prisoners of war, veterans exposed to certain toxic substances and radiation, pensioners and veterans of wars prior to World War II. Other veterans are eligible for free care if their income falls below certain levels, $20,000 a year for single veterans.

The VA operates the nation's largest medical care system, with 172 hospitals and hundreds more nursing homes and other clinics.

Most of the VA's budget goes for veterans benefits and medical care. The proposal also would authorize more than $500 million in construction of new or renovated medical facilities, including major projects in Dayton, Ohio; North Chicago, Ill.; Palm Beach, Fla.; Atlanta; Montgomery, Ala.; Prescott, Ariz.; Huntington, W.Va.; and Jackson, Miss.