Roman Catholic bishops this week begin debate on a pastoral letter that says that the United States has a moral obligation to ensure that no one is hungry, homeless or unemployed.

Wealth is so unevenly distributed in the United States that it does not meet the "minimum standard of distributive justice," and there must be a greater transfer of wealth to the poor, the letter said.

A draft of the proposed pastoral letter was released yesterday by the National Conference of Catholic Bishops, a day before a week-long meeting begins here. The draft's publication starts what is expected to be a yearlong debate among Catholics prior to the bishops' anticipated final vote on the pastoral letter next November.

Written by a committee of five bishops headed by Archbishop Rembert G. Weakland of Milwaukee, the 136-page draft was couched in moral rather than political language as a bill of rights for the poor and jobless.

Unlike civil rights, "economic rights" -- adequate nutrition, housing and employment -- do not hold a "privileged position" in the United States, the drafters said.

The bishops called on the nation to frame "a new national consensus that all persons have rights in the economic sphere and that society has a moral obligation . . . to ensure that no one among us is hungry, homeless, unemployed or otherwise denied what is necessary to live with dignity." To meet these basic needs, there must be a larger transfer of wealth from the richest in America to those less well-off, the bishops said, citing biblical warnings of the moral peril of great wealth.

"The distribution of income and wealth in the United States is so inequitable that it violates the minimum standard of distributive justice. In 1982 the richest 20 percent of Americans received more income than the bottom 70 percent combined," the bishops said.

While recognizing the right of individuals to amass wealth and property, the bishops warned against the temptations of "indifference and greed," saying these "sins . . . continue to block efforts to secure the minimum economic rights of all persons."

"Certainly in Catholic society, there is a tendency to try to measure one's worth by the accumulation of luxury goods. Those temptations are out there," Weakland said. "Wealth can be a danger."

By the same token, the United States has responsibilities to poor nations that it is not now meeting, the bishops said.

The draft letter, three years in preparation, was deliberately withheld until after the presidential election because the bishops said they did not want it to be seen as politically motivated.

At a news conference yesterday, Weakland was asked if he was troubled by President Reagan's campaign theme suggesting that Americans cast their ballots on the basis of whether they are better off now than four years ago.

"To me, the real question . . . as a religious leader and preacher of the gospel I would have to ask is what you're doing with your money now that you're better off . . . . Because we are better off, we realize our obligation to those who are less fortunate," Weakland said.

The Catholic Church "is no longer an immigrant church," said Bishop Peter A. Rosazza, auxiliary bishop of Hartford, Conn., and an author -- with Weakland and Bishops Thomas A. Donnellan of Atlanta, George H. Speltz of St. Cloud, Minn., and William K. Weigand of Salt Lake City -- of the draft letter.

The church's teaching has not kept up with the fact that many Catholics have moved from "working class" status into positions of power and leadership in society, he said. It is to these in particular that the letter appears to speak.

The letter calls for a major commitment to reduce unemployment to 3 to 4 percent -- roughly half recent levels -- through government employment programs targeted on the long-term unemployed and private job-training programs.

It asks for tax reform to "reduce the burden on the poor" and a range of efforts to improve educational, child care and job opportunities for the poor and minorities. Its proposals, however, concern broad goals rather than specific strategies.

For the "woefully inadequate" welfare system, the letter recommends national eligibility standards, a national minimum benefits level, and that welfare policies be changed to strengthen, not weaken, the family.

Weakland recollected spending many years on welfare in Patton, Pa., after his father's death in 1932, when Weakland was 5. The focus of welfare and employment programs must be to help people become independent and self-supporting again, he said.

He recalled the day as a high school student when he brought his first paycheck home to his mother. At that moment, he said, "I grew up. That gave me a whole new way of seeing life. I became a participant, a contributor, and I felt my own dignity."

The achievement of "economic rights" requires not only charity but a greater sharing of economic power and opportunity, the bishops said: "Justice is not simply a matter of seeing to it that people's private needs are fulfilled. It is also a matter of enabling them to be active and productive."

In many of their important recommendations, the bishops stand clearly on the side of labor-union leaders and liberal academics who want employes to have a stronger voice in such decisions by management as closing or relocating factories and offices.

It recommends closer cooperation among management, labor and the banking community to create employment in economically distressed areas and to save as many jobs as possible in declining industries.

But the bishops appeared intent on taking a position between the extremes of centralized, national economic planning, and a hands-off, laissez-faire model of unregulated competition.

"We are well aware that the mere mention of the notion of economic planning is likely to product a violent allergic reaction in U.S. society," the letter said. "What the church calls for is "a balance between individual initiatives and the common good.

"To turn aside from those on the margins of society, the needy and the powerless, is to turn away from Jesus, who identifies Himself with them," the letter continued. "Such people present his face to the world."