Congress has voted to restore the District of Columbia's right to borrow from the U.S. Treasury to fiance the city's construction program.

The Senate agreed Tuesday to accept the House-passed version of the borrowing legislation and sent the measure to the President for his signature.

Without the legislation, the city would be unable to spend $100 million to build or repair schools, office buildings, sewers, libraries and other facilities during the 1978 fiscal year, which began last Saturday.

The District's century-old right to borrow from the Treasury substanially lapsed with the start of home rule in 1975, and was kept alive on a year-to-year basis by special language added by Congress to the city's annual budget bills.

Such language in the 1978 budget was knocked out on a parliamentary technically by Rep. Robert E. Bauman (R-Md.) who was seeking to block a loan of $27 million to start work on a downtown convention center.

The congressional enactment of the separate borrowing legislation clears the way for restoring those other projects and possibly the convention center.

House and Senate conferees will meet next Wednesday to resolve differences in the versions of the city budget approved by both chambers. The House voted to support the convention center, while the Senate rejected it.

About the District Building yesterday, about a dozen of the strongest supporters of the convention center, including leading businessmen and top city officials, met for about two hours in Mayor Walter E. Washington's office to discuss possible strategies for salvaging the project.

No firm decisions were made, however, and afterwards when one participant was asked what leverage the center's backers would have in the House-Senate conference committee he responded, "Damned if I know. I just don't know."

One city official who attended the meeting said that the group has rejected any possible scaling down of the proposed project in order to satisfy critics who contend that the cost is too high.

Also rejected was the idea that the city's business community, which has long championed the project, could put up additional money to lower the center's cost, several participants said.

The group appeared yesterday to be placing its highest hopes on the ability of Rep. William H. Natcher(D-Ky.) to prevail in the conference and, despite an apparently lopsided rejection in the Senate and a razor thin margin of victory in the House, they remained optimistic that the project would be approved.

Among those city officials at the meeting were the mayor. City Administrtor Julian R.Dugas, City Pallnning Director Ben W. Gilbert and City Council Chairman Sterling Tucker. Most of the businessmen present were affiliated in some ways with the Metropolitan Washington Board of Trade, and included Joseph B Danzansky, Clarence Arata, Foster Shannon, R Robert Linowes and Robert B Washington Jr.