NASHVILLE, JUNE 15 -- Three Democratic presidential candidates sought support among the nation's mayors today, calling for initiatives in housing, education and, in one case, a public works program financed by pension funds.

In the first of three days of appearances by presidential candidates, the 55th annual Conference of U.S. Mayors heard from Jesse L. Jackson, Massachusetts Gov. Michael S. Dukakis and Rep. Richard A. Gephardt of Missouri.

Jackson charged that federal budget deficits draw off funds that could finance urban programs and proposed that cities and major unions join to pool portions of their pension funds for investment in public works projects.

"Think of yourselves and . . . the country's top 10 union leaders as an urban cartel, the OPEC of investment capital," Jackson said. He argued that such a fund could be used to finance housing for the homeless, roads and other public investments without "pouring the hard-earned savings of America's public workers down the drain."

But at a news conference later, he did not explain how such investments would produce a return to the pension funds, saying "some of that detail is going to have to be resolved."

Dukakis, stressing the revitalization of Lowell, Mass., and other once-beleaguered Massachusetts cities, outlined his plans to provide homes for low and moderate-income families, prevent conversion of existing low-income, public housing into more-expensive rental apartments and condominiums, and expand "opportunities for home ownership for young and first-time home buyers."

He provided neither a price tag nor details of this program, describing it instead as a "national partnership" between cities, states and the federal government.

Gephardt reiterated proposals to require that all children receiving welfare attend a Head Start program or the equivalent beginning at age 3, to require pregnant women on welfare to participate in prenatal and food supplement programs, and to provide federal subsidies for high-tech training devices in poor school districts.

Like Dukakis, Gephardt said he does not know what the cost of his programs would be, and he acknowledged that the deficits of the "Reagan years . . . have left us with a limited range of choices."

Gephardt and Dukakis held separate breakfasts for the mayors, at which the two candidates voiced similar declarations of support for programs close to the hearts of local politicians, using the vernacular of urban administrators:

"I am an advocate of CDBGs. I am an advocate of UDAGs," Gephardt declared, and Dukakis said, "I am a guy who believes in UDAGs and believes in CDBGs." The two programs -- urban development action grants and community development block grants -- have faced cuts under the Reagan administration.

In terms of concrete political developments, the most significant event today was a declaration by Chicago Mayor Harold Washington that he will not attempt to field his own set of delegates in Chicago in the Illinois primary.

Most presidential strategists say the decision means Washington has effectively ruled out using his popularity among black voters to help any of the white presidential candidates, thus sharply improving Jackson's prospects in the city. Washington, who backed Jackson in 1984, did not dispute this interpretation.

New Orleans Mayor Sidney Barthelemy indicated he will back Jackson; St. Paul, Minn., Mayor George Latimer signaled that he is likely to support Dukakis, and Minneapolis Mayor Donald M. Fraser has signed on with Sen. Paul Simon (D-Ill.).

Detroit Mayor Coleman Young would not say who he will support, but he flatly ruled out backing Jackson. "I'm not interested in a protest vote, I'm interested in a winner," he said.