Roman Catholic leaders yesterday launched a two-year program aimed at staving off serious financial problems faced by the church's religious orders, with their growing numbers of elderly priests and nuns who have given their lives to the church and now lack resources for their retirement care.

But the heads of three national agencies, including the National Conference of Catholic Bishops, admitted they have not figured out how to raise the $2.5 billion that a newly completed study says is needed for the task.

The retirement crisis "developed over many decades," said Sister Lora Ann Quinonez. "Solving it will pose a genuine challenge" requiring "the best efforts and imagination of all segments of the church." Quinonez is executive director of the Leadership Conference of Women Religious, which, together with a counterpart organization of men's religious orders and the bishops' conference, jointly sponsored the nationwide study of the problem.

According to that study by Arthur Andersen & Co. released this week, the total cost of funding the needs of those already retired and establishing pension plans for men and women currently in active service is $2.5 billion -- of which more than 80 percent is needed by the women's orders.

The combination of longer life expectancy and a sharp drop in the numbers of young people choosing lives in the church has produced disproportionate numbers of elderly priests and nuns. There are fewer and fewer young priests and nuns to support their elders in retirement.

Sister Mary Oliver Hudon, academic dean of Notre Dame College in Baltimore, outlined the goals of the new program, which she will direct beginning July 1. She said yesterday that it would involve "an educational program for all the church," the provision of emergency funds for religious orders facing immediate problems, "the design and collection of models" of retirement programs and the development of "fund-raising strategies."

Pressed on how the needed $2.5 billion would be raised, Hudon said "a variety of different solutions" will be sought, including the possibility of "a national collection" on a given Sunday. Given the church's current 52.6 million members in this country, it would require a contribution of a little more than $47 from every Catholic adult and child to raise the $2.5 billion from this source alone.

Msgr. Daniel F. Hoye, general secretary of the bishops' conference, warned against viewing the problem in terms of "good guys and bad guys . . . . This is a very complex situation with a lot of factors contributing to it."

Quinonez pointed out that "the American Catholic Church had its origins among poor immigrants . . . who relied heavily on the fact that it was possible for [religious] sisters and brothers to work for very little" in developing schools and hospitals.

The three conferences of bishops, nuns and religious orders of men have been trying for nearly six years to get a handle on the retirement crisis, Hoye said. During that time, they have developed teams of expert consultants that can help individual orders analyze their situation and restructure their finances to make the best use of their facilities.

He said that 90 religious communities have requested such help.

Another source of the retirement crisis has been the traditionally low pay for nuns teaching in church schools. Hoye said yesterday that the bishops want to remedy that, and in fact, the bishops' forthcoming pastoral letter on economic life reminds bishops that they must practice in their own institutions the economic justice they preach for others.