Kennedy Center Chairman Roger L. Stevens said yesterday that the proposal to extend the north and south ends of the Kennedy Center 60 feet to house a new conservatory has been "abandoned."

But a proposed new parking garage on the triangle of land east of the present building is still under consideration, with the possibility that a one-story conservatory or "academy" of reduced size could go on top of it.

"We have had to abandon the entire original project" of three new buildings, Stevens said, "because our plans of empire are beyond our means today.

"We got the construction estimates this week and no one was prepared for what they were like," said Stevens. "We were talking about something in the area of $20 million-$25 million, and what we got was $58 million-$65 million as the current cost. There's no way I'm going to raise that kind of money. Apparently a parking stall alone costs $20,000 now and we need 500 more of them. "

Architect George Hartman, partner in the Hartman/Cox firm here, had proposed three new building projects: the center's extensions; a buried triangular parking lot on the east side; and a relatively small structure for student housing at the western corner of the plot. The proposal had been presented to the Fine Arts Commission in November.

Stevens said he has asked the architects to prepare new construction estimates on the revised east building and to build a new model. "Then we'll be able to decide whether we can afford any kind of academy at all. If so, it would be a reduced one that would work with about 100 fellows in music and theater." The conservatory would have had about 300,000 square feet in the old plan and would have about 100,000 square feet in the new proposal.

Hartman said yesterday, "There was only enough money to do half of a symmetrical design . . . and you can't do half a symmetrical scheme."

The idea of a conservatory in Washington has been pondered for almost a century. Stevens revived it this fall, packaging it with a solution to the center's acute parking problem. The center garage, as originally built, ended up with a shortage of about 250 spaces in the underground garage on a full night, thus sending many last-minute arrivals to other neighborhood facilities.