Suburban Maryland officials told the state's congressional delegation yesterday they want the federal government to assume all the costs of accommodating Cuban refugees in the area.

Between 2,500 and 5,000 Cuban refugees are expected eventually to settle in Montgomery and Prince George's counties, officials informed seven congressmen and Sen. Charles MACTHIAS (R-Md.).

Providing housing, job assistance and welfare services for the refugees "will put a strain on already scarce resources," said Harvey McConnell, director of the Montgomery County Office of Family Resources.

Without congressional aid, McConnell said, "the locations may have to put up money, and many cities don't have any money to spare.Local people will resent the expense and they'll resent the Cubans too."

Members of Congress at the meeting said the House passed a $100 million appropriation this week intended to aid state and local governments in handling the refugee influx. The Senate has yet to act on the bill.

The House legislation, proposed by the Carter administration, would provide only 75 percent reimbursement for local refugee-related expenses.

"Because we don't know how many people our agencies will handle, we don't really know how much this is going to cost. We will need all the help we can get," said Wilbert Wilson, senior assistant to Prince George's County Executive Lawrence J. Hogan.

Officials admitted that they cannot say with certainty how many refugees have arrived in the Washington area or how many plan to come. One informal estimate, made for a reporter by a volunteer for a Northern Virginia agency later yesterday, is that perhaps 20,000 will come to the metropolitan area.

"Part of the problem is that there is no single place where all refugees are referred to, so we can't really get an accurate count," Wilson explained. He said Hogan recently requested state aid from Acting Gov. Samuel Bogley to establish a refugee referral service.

The county officials estimated that thus far approximately 150 refugees have settled in Montgomery County, and about 75 in Prince George's. Most of the refugees expected to settle in the Washington area are awaiting processing at the Indiantown Gap relocation center in Pennsylvania.

Most of the Cuban refugees are coming because they have friends or relatives in the area, officials say. An estimated 10,000 Cubans live in the Washington area, about half in Montgomery County.

So far 500 persons in Montgomery County, most of them Cuban, have agreed to sponsor refugee families, according to McConnell. Based on an estimate of four members per family, McConnell said he predicts at least 2,000 refugees and perhaps as many as 4,000 to settle in the county.

Wilson said Prince George's County expects between 500 and 1,000 refugees to settle in the Langley Park area, which already has a sizeable resident Cuban population.