The District of Columbia government yesterday was given more time to come up with a plan for building a new campus for the fledgling University of the District of Columbia in hopes that such a plan can win approval of the Senate Appropriations Committee.

Congress appropriated $56.7 million for construction of UDC buildings two years ago. But because the work has not yet begun, the authorization would have expired Sunday, at the end of the fiscal year, if the Senate Appropriations Committee had not acted yesterday.

Sen. Patrick J. Leahy (D-Vt.), chairman of the D.C. Appropriations subcommittee, proposed a one-year extension of the authorization, but urged the city to come up with an acceptable plan within 90 to 120 days.

Release of the funds is contingent upon approval of the building plan by both the Senate and the House. The current proposal is not favored by Leahy, who has virtual veto power over release of the money.

The city and UDC officials want to build two campuses, one downtown at Mount Vernon Square, and another, already under construction with previously appropriated funds, on upper Connecticut Avenue, called the Van Ness Campus.

Although the House has approved the dual campus proposal, Leady told the Senate committee that the current plan is "deficient on a number of accounts." He said his nose count of the 28-member committee found "at least three or four votes" for the two-campus idea.

"So I strongly urge a new plan, ideally for a single campus," Leahy said, "I may be able to sell that, although there is no guarantee."

Mayor Marion Barry said he was "grateful" to Leahy for getting the extension but that he remains committed to "working toward completion of a downtown UDC campus."