As part of its new round of budget cuts, the Reagan administration is considering sizable cuts in the welfare program for the aged, blind and disabled, one of the "social safety net" programs the president said would not be cut last spring.

The White House is also considering further cuts in the more familiar welfare program, Aid to Families with Dependent Children. And it is studying proposals under which, for the first time, poor people could be required to pay part of the cost for basic medical care under the Medicaid program.

President Reagan said two weeks ago that, to keep the deficit down, he would ask Congress to approve another $13 billion in spending cuts for the fiscal year that began Oct. 1. He said nearly $3 billion of these would come in the government's basic benefit or entitlement programs, but did not specify how they would be achieved. Now sources say the specific entitlement cuts will be sent on to Congress next week.

A list of possible cuts was compiled this week in a secret report by a special budget task force in the Department of Health and Human Services.

Among potential reductions it mentioned were: cutting the current $264.70 monthly federal payment to aged welfare recipients by up to $85 a month in some cases; limiting AFDC payments to four months when an unemployed father is present in the home; rewriting the rules to cut the benefits of elderly recipients who live with relatives or friends and do not pay rent.

If all the changes in the task force list were actually adopted, it could mean eventual cuts in AFDC and Supplemental Security Income--the welfare program for the elderly, blind and disabled--of an additional $2.3 billion a year, or one-sixth of total current costs, on top of the $1 billion in AFDC cuts adopted by Congress in last summer's budget bill at the administration's request.

HHS is also looking at options for major new cuts in Medicaid for the poor and Medicare for the elderly and disabled which could force recipients to pay more out of their own pockets.

One proposal reportedly under study is to charge Medicaid patients at least $1 for each day they are in hospital; another is to charge Medicare patients $1 or more daily for the first 60 days in hospital. Medicare patients now pay an initial hospital deductible but remaining hospital costs for the first 60 days are free. These new cuts would be on top of about $2 billion a year already cut from Medicaid and Medicare by the budget bill.

Laura Genero, a representative of HHS Secretary Richard S. Schweiker, said no final decisions to ask Congress for any of these cuts has yet been made, and she called the task force report "simply a list of options" drawn up by "lower level" bureaucrats, some of which have already been discarded. She declined to discuss details.

However, other sources said many of the ideas probably would end up being approved.

According to department sources, the objective is to have all changes in effect by next April 1. That means that in fiscal 1982, any savings would have only about half the full-year impact.

Among possible cuts laid out by the task force:

* Permit the states to pay AFDC to families with an unemployed father present only for four months. About half the states now make payments to such families and for as long as the family is in need; the others make payments only to families where the father is absent. About 776,000 of the 11 million AFDC recipients are in unemployed-father families, largely in big industrial states like Michigan, Ohio, California and New York. Both Maryland and the District of Columbia are also in the program. Full-year federal saving, $350 million.

* Cut AFDC benefits where recipients are living within larger households and can be deemed to get free shelter and utilities. Saving: $350 million.

* Freeze at 1981 level the average federal reimbursement level to states with high AFDC benefit levels. $350 million.

* Cut off the parent's benefit when youngest child reaches 16 (instead of 18). $75 million.

* Deny extra federal reimbursement for any children after the first four. $120 million.

* Round SSI payment to next lowest dollar and stop paying SSI back to the first of the month when people apply in the middle of the month. $100 million.