Housing and Urban Development Secretary Samuel R. Pierce Jr. reportedly told HUD regional administrators meeting here recently that he plans to leave his job soon.

Rumors that Pierce wants out have been circulating for many months, but sources inside HUD say the most recent round has "good grounding" and is "more than a rumor."

Sources said that while a number of Reagan administration officials do not consider Pierce to be a strong secretary, no movement is afoot to force him out. Instead, they say, it is Pierce who wants to leave.

But a HUD spokeswoman said Pierce did not tell the regional administrators or anyone else that he is leaving. "What he said was, there are several things he has to finish that are very important to him," and then he will decide what he wants to do, said Jayne Gallagher, HUD's director of public affairs. "It's the way he phrases it" that caused Pierce to be misunderstood, she said.

Names being circulated at HUD as most likely to succeed Pierce include Maurice L. Barksdale, former assistant secretary for housing and federal housing commissioner, and Robert Woodson, head of the Center for Neighborhood Enterprise here. Both men are black.

UPDATE ON UDAG . . . Pierce has announced the recipients of the last batch of Urban Development Action Grants (UDAG) that can be awarded until Congress decides the fate of the popular program, which the Reagan administration wants to kill.

A total of $56.3 million will be distributed among 42 commercial, industrial and neighborhood projects in 32 large cities.

The Senate Banking, Housing and Urban Affairs Committee recently approved a bill that would extend the program for two years, authorize $744 million for it, and widen the criteria for selecting grant recipients. The eight-year-old program provides grants to economically distressed cities and urban counties for commercial, industrial and neighborhood development projects.

The Senate bill was a "major victory" for supporters of the program, said an aide to Sen. Donald W. Riegle Jr. (D-Mich.), who has been a leader in efforts to rescue the program. The bill would provide $366 million in fiscal 1986 and $378 million the following year.

The House Banking, Finance and Urban Affairs Committee also voted to extend UDAG, and to broaden the selection criteria, in the housing authorization bill it approved in July. The bill is still awaiting floor action.

Under the current selection formula, more than half of all UDAG grants awarded in the past two years have gone to only nine states. Fifteen of the 39 projects funded in one group of grants were located in New York and New Jersey, and only one state west of the Mississippi received any funds, according to Sen. Charles E. Grassley (R-Iowa), who supported extending the program, but wanted the criteria changed. Grassley said several Iowa communities "were consistently bypassed for UDAG grants."

The Reagan administration argues that the economic recovery and funding now available from state and local budget surpluses makes the UDAG program unnecessary. Administration officials also argue that the federal government should not interfere with private-sector development.

Among the grants announced in the latest round was a $736,346 grant to a minority nonprofit organization in Baltimore to help construct a health and day-care center for the elderly.

If Congress votes to extend UDAG, cities with populations under 50,000 will receive the first group of awards from the fiscal 1986 budget in early December, and grants for large cities and urban counties will be announced in January, according to HUD.

FUNDS FOR PUBLIC HOUSING . . . HUD has backed away from a proposed rule change that critics said would have restricted the ability of public housing authorities to manage their funds, after the Senate Appropriations Committee told the agency that Congress wanted a chance to review the rule.

The authorities are required to hold an amount equal to 20 percent of their operating budget as a reserve fund. HUD wanted to keep that money in the federal treasury, disbursing it only as needed, instead of letting the housing authorities invest it themselves.

The Appropriations Committee's report said the planned rule would encroach on the rights of public housing authorities to manage their money.