Mayor Marion Barry's delicately balanced plan to close the District's budget gap showed signs of problems yesterday as the prospects for some pivotal revenues became uncertain and city officials sought less controversial alternatives to some of the spending cutback proposed by Barry.

There were strong indications yesterday from the City Council, from Capitol Hill and from within the Barry administration of imminent problems:

Council member John A. Wilson (D-Ward 2) chairman of the Council's taxation committee, said through an aide that Barry's $20.2 million tax package "could not be rushed through" the Council and may not be approved by May 1.Barry has said that without approval by that date, he will begin immediately to lay off police officers, firemen and other city employes -- perhaps as many as 5,000.

Earlier in the week, Wilson said he did "not have the slightest idea" when he would hold hearings on the tax proposals. "I'm in no hurry to do that," Wilson said. "I have to see what kind of support there is. Right now, we don't have the support on the council for it."

As influential source on Capitol Hill, who asked not to be identified, said "it's not very real" for the mayor to expect to receive all $61.8 million requested through a supplementary federal payment.

Granting that request would push the federal payment to record high amounts during a time of federal fiscal austerity, the source said. Moreover, some members of Congress are upset because the Barry administration is already spending at levels that assume the full request will be granted.

"That's putting the cart before the horse. For planning purposes, that's not very smart," the source said. "We're not too pleased about that kind of attitude."

D.C. Corrections Director Delbert C. Jackson said yesterday that he could not lay off 360 people in his department -- including dozens of guards -- as Barry has proposed.

"That would make our circumstances intolerable. There's no question, I could not live with that," Jackson said. Yesterday he talked with city budget officials to find ways to cut spending without the layoffs.

"It will not be 360," Jackson told a reporter. "I can assure you of that."

Budget Director Gladys W. Mack said yesterday that the administration was still confident that its plan would work. She would not say how much of the $61.8 million supplementary payment she expects to be approved. "We will get a positive response," she said. Hearings on the request are to begin before a House subcommittee on Thursday.

Although Barry has emphatically said he will begin massive layoffs on May 1 if his tax package is not approved, Mack asserted yesterday that the deadline should not be taken literally.

"The May 1 deadline is a guide which the mayor put there so that he can have a sense of where the Council is," she said. "If the Council schedules its action in such a way that by May 1 the mayor knows he can get some action out of the Council, I think that satisfies the May 1 deadline."

Barry had planned to reduce spending in the Corrections Department by $45 million, largely through 360 layoffs, 40 staff reductions through attrition and closing the century-old D.C. Jail annex May 1.

Mack said yesterday that the jail annex might be kept open an additional month and some of the layoffs may be avoided if other ways to save money are found. "A week ago, we didn't have the additional information we have not," she said.

At one point, it was planned for the first of the layoffs to become effective April 1. But Jackson said yesterday that no notices of layoffs have been sent out yet.

William H. Whitehurst, acting director of the Department of Human Services, where more than 100 layoffs were also to take place, said that he, took, has not sent out any notifications. Whitehurst said he could not be sure how many jobs would be eliminated in his department until the Council acts on the tax package. "It could be up, it could be down," he said.

Late last week, the administration reversed itself on an initial plan to save $153,000 by closing 21 after-school recreation centers. City Administrator Elijah B. Rogers, acknowledging that Barry was concerned about citizen opposition to the plan to close 21 centers, announced instead that only 10 would be shut down for a savings of $72,000.

Initially the administration planned to close centers in every ward except Ward 3, the mostly white and affluent section of the city west of Rock Creek Park. Barry's final plan calls for closing of centers in all wards except Wad 3 and Ward 8 -- the mostly black and poverty-ridden section of the city in far Southeast Washington.

Not closing the other 11 centers means the Barry administration will have to find other ways to save $81,000 if the budget balancing plan is to succeed.

The Barry tax package includes a new 6 percent tax on gasoline sales, a new 5 percent tax on professional and trade services, a 30-cent increase in the tax rate for commercial properties and increases in the tax rates for deed recordation, hotel rooms and business personal property.

Brigid Quinn, executive assistant to Council member Wilson, said yesterday that it is still unclear how much revenue would be raised by the new taxes, who woul be exempt from paying them and whether the package could be approved by May 1 without bypassing present city regulations.