The vice chairman of the Postal Service Board of Governors charged yesterday that African Americans are "overrepresented" on the postal work force in a number of large cities and Hispanics are seriously underrepresented.

Tirso del Junco, a Los Angeles surgeon, blamed black postal managers in those cities, saying they had made few efforts to find qualified Hispanics and preferred to hire black workers. "They think it is a right to have this overrepresentation," del Junco told reporters.

Postal officials did not dispute del Junco's assertion that the agency needs to hire more Hispanics, but they denied any effort to slight Hispanic job applicants. The agency's hiring practices are colorblind and not designed to help or hurt any minority, officials said.

The vice chairman's remarks, which occurred at the monthly governors' meeting after the release of a report on Hispanic hiring, were an example of the tension between blacks and the growing Hispanic community over access to government programs and jobs. In the District, Arlington and other communities, Hispanic leaders have alleged that government officials pay too much attention to the needs of the larger black community and too little to the needs of Hispanics.

Shortly before del Junco made his remarks, Postmaster General Marvin T. Runyon publicly acknowledged that the Postal Service needs more Hispanic employees. "I feel strongly about this issue and I want to assure you that we are committed to making progress in affirmative action and being a leader in work force diversity," he told the postal board.

Nationally Hispanics account for 6.4 percent of the Postal Service work force compared with 8.1 percent of the nonmilitary work force. Blacks account for 20.8 percent of the postal service work force, double their representation -- 10.3 percent -- in the national labor force.

But when individual communities are compared the disparity grows. A report given to the board yesterday and based on data compiled by the General Accounting Office showed the number of Hispanic postal workers in Los Angeles and Chicago fell well behind their comparable numbers in the civilian labor force in each city.

In Los Angeles, for example, blacks account for 63 percent of the postal work force, compared with 9.6 percent of the nonmilitary labor force. Hispanics make up 34 percent of the Los Angeles area labor force but account for 15 percent of the Postal Service work force. In Chicago, blacks account for 79.7 percent of the postal work force, compared with 18.2 percent of the general labor force. Hispanics in Chicago account for 3.9 percent of the postal work force and 11 percent of the overall work force.

In the Washington area, blacks make up 86.4 percent of the postal work force; Hispanics account for 1.1 percent. The Postal Service did not release figures for local civilian employment by race yesterday.

A six-year member of the postal board, appointed by President Ronald Reagan and reappointed by President George Bush, del Junco repeatedly has berated postal managers for not hiring enough Hispanic workers. A Cuban native, del Junco is also a Republican National committeeman from California. His latest statement was one of his sharpest, and he coupled it with allegations that post offices in major cities have disproportionately too many black workers.

Del Junco told the board that Hispanics and white males have suffered as a result of the disparities in hiring. "The amount of discrimination against white men in some cities is incredible," he told his fellow governors.

The hiring, he said several times, is "not a racial, not an ethic issue" but one of equity for Hispanics. Del Junco said he is trying to get more jobs for Hispanics because postal jobs are among the best jobs in the country.

LeGree S. Daniels, the only African American on the postal board, disagreed sharply with del Junco's charges that African Americans were overrepresented on the postal work force. Daniels acknowledged concern about the agency's failure to retain the relatively small numbers of Hispanics it has hired in recent years, but she said that among government agencies, the Postal Service was "the pioneer" for hiring minorities.

"Long before the civil rights laws, there was the post office," she said in an interview after the board meeting. "It was the place where you went to get hired."

Charly Amos, the agency's manager of affirmative action, said that in many areas of the country that tradition remains with strong "networks" of black community leaders who actively urge blacks to apply for postal jobs.

Workers are hired off a register of job applicants who have passed a written examination and the rules for hiring are rigid, he said. Any manager who would attempt to manipulate the hiring process "could get fired," Amos said.

Angelo Wider, executive vice president of A-Plus, an organization of 3,000 black postal executives, said his organization was "not opposed to Hispanics being represented. We think there is enough to go around." Like Daniels, Wider disputed del Junco's remarks that blacks were overrepresented in large cities.