Members of a House subcommittee said yesterday they plan to rearrange $27 million in the District of Columbia's tight fiscal 1984 budget to pay for street lighting and to force the city to pay off more of its long-term debt.

Unless Congress decides to add more federal funding at the same time, the city will have to cut the $27 million from other programs, which already have been sharply reduced in many areas.

This would pose an "unworkable problem" for the city if Congress insists on it, Alphonse G. Hill, deputy mayor for finance, told the panel. But the subcommittee members showed no sign of being moved.

Rep. Julian C. Dixon (D-Calif.), chairman of the House Appropriations subcommittee on the District of Columbia, told city officials at a hearing yesterday that he does not believe they can count on $12 million in savings next fiscal year from a plan to turn over the cost of street lighting to Pepco and ultimately, through rate increases, to Pepco's customers.

The fiscal year begins on Oct. 1, and Dixon said it will take longer than that to accomplish the change, particularly since Pepco has threatened to fight it in court. The change requires action by the Public Service Commission.

"This seems to be a highly controversial issue that has not moved forward," Dixon told Thomas Downs, D.C. transportation director.

Downs replied that the city believes it can get the PSC to approve the required changes before the fiscal year begins, and city budget director Betsy Reveal said the city's petition to the PSC will be filed within two weeks.

"If we don't budget for it, it won't happen," Downs said. By assuming the $12 million change in the budget, the city adds pressure for quick action on the plan, he said.

But Dixon remained unconvinced.

"It's like putting a gun to your head and saying you're going to get something done because your life is in peril," Dixon said of Downs' logic after the hearing.

Dixon said he will talk with D.C. officials about where they want to make cuts to pay for the street lighting. If they do not want to identify other cuts, Dixon said, he will look first to using money from the federal payment to the city.

The federal payment in fiscal 1984 is supposed to rise to $386 million, $25 million more than this fiscal year, under a request by the Reagan administration. Mayor Marion Barry has said he wants to commit the $25 million increase to retirement costs, D.C. General Hospital and St. Elizabeths Hospital.

Rep. Lawrence Coughlin (R-Pa.), ranking minority member of the subcommittee, said the city also should identify another $15 million for reducing its long-term deficit of $296 million. The city put only $5 million in its budget for this purpose.

The subcommittee last year had insisted the city spend $20 million this fiscal year to retire its debt, though city officials say they may not be able to set that much aside. Dixon said he has not made up his mind whether $20 million should be required again next fiscal year.