A small group of black politicians and civil rights leaders today called for a black candidate for the 1984 Democratic presidential nomination but postponed until at least this fall endorsement of such a candidate.

Instead, the group decided to concentrate on a massive voter-registration drive to build a coalition with women, Hispanics and other minorities and on winning grass-roots support for a 120-page "people's platform" drafted to represent their constituents' political concerns.

The decision by about 20 persons meeting here provided a limited victory for the Rev. Jesse Jackson of Chicago, who is considering running for president and would prefer to do so with the support of most other black leaders.

The group's decision not to criticize or disown Jackson's potential candidacy enables him to avoid the political liability of being seen as a loner.

Jackson, who attended the five-hour meeting, said later that an exploratory committee headed Mayor Richard G. Hatcher of Gary, Ind., has been formed to interview potential candidates. Hatcher, one of two big-city mayors here today, is a Jackson supporter.

However, the committee has no formal connection with the ad hoc group that today met for the fourth time since February.

Jackson said that he has not decided whether to run but that the group's action increases the chance that a black candidate will emerge for 1984. He is the only black being mentioned seriously as a candidate.

The platform adopted today also provides a safety valve for many of those who had attended meetings of the ad hoc group but were pledged to support one of the six announced Democratic candidates, all whites, or were opposed to endorsing Jackson, who has never held elective office and has sometimes been considered a maverick.

The document is expected to give those opposed to a black candidacy an agenda for urging white candidates to be more sensitive to black concerns. That was among the major goals cited for a black candidacy when the group's meetings began.

"Initially, we thought we could put together a process for a consensus that would have been completed by June," said Del. Walter E. Fauntroy (D-D.C.), spokesman for the coalition, after today's meeting. He was the only member of Congress present.

"What we have concluded," he said, "is that . . . in the absence of a serious effort to mount a candidacy, it is not likely you could meet a broad consensus on such an effort and that such an effort is not likely to have the unanimous support of the black community . . . . All black leaders do not feel that the advantages outweigh the possible disadvantages."

Fauntroy said that a black candidacy would encourage voter registration and underscore blacks' ability to run for the nation's highest elective office. He said that the group decided today to structure itself more formally as the "Black Coalition for 1984" and to seek grass-roots national approval of its platform.

That platform seeks, among other things, full employment, increased spending on human-development programs and smaller federal deficits through cuts in military spending and tax reform.

It also seeks a nuclear freeze, a foreign policy based more on development aid and less on militarism and a reversal of what is viewed as a retreat on civil-rights law enforcement.

The group decided to launch an effort to increase black voter registration 25 percent in 24 key states.

Jackson said that, if he decides to run, his candidacy will not be that of a national "favorite son" trying to maximize black influence at the Democratic National Convention as most black leaders have discussed.

"If I choose to run, I would have to program myself for 1600 Pennsylvania Avenue . . . if I make a decision, it will be based upon a calculated program for winning it all. I do not see how anyone can run for the White House by preparing to sleep in the outhouse," he said.