The D.C. government has been forced to defer more than $45 million in construction and renovation projects planned for the coming year because of limitations imposed by the Reagan administration on the city's authority to borrow from the U.S. Treasury.

All funds for renovation of Barry Farms and East Capitol Dwellings public housing projects, all money for street and sewer improvements in the Capitol Gateway Development area of Southeast Washington, and funds for a new ambulatory care center at D.C. General Hospital have been cut out.

Construction of a new police and fire harbor station on the Maine Avenue waterfront has been deferred. A start on building a new municipal office building has been put back by at least a year, and the renovations of Eastern and Coolidge Senior High Schools have been postponed.

Mayor Marion Barry, in a letter to City Council Chairman Arrington Dixon, said that "the impact of the proposed limit on the District's capital program is extensive. Major renovations, critically needed building rehabilitations, modernizations and replacements will have to be delayed."

The District government borrows all construction money from the U.S. Treasury, unlike other cities which finance capital projects through bond sales. In the fiscal year that starts Oct. 1, the city was planning to borrow $219.4 million to finance projects previously approved by congress. But the Reagan administration notified the city in March that drawdowns of only $145 million would be permitted.

That decision forced the city to reduce its projected construction spending by $74.4 million. Revising the city's obligation to regional Metro transit construction for next year trimmed $28.6 million, but the rest had to be shaved from D.C. projects on which work was scheduled in the coming year.

A major chuck -- $13.1 million -- was trimmed from the spending program by deferring once more a start on construction of a new municipal office center. That decision was expected, since no site has been selected. Another $13 million was cut by deferring some work on the new crosstown water main. The remainder was trimmed in bits and pieces from road projects, sewer and water works, street and bridge repairs, school renovations, Lorton Reformatory improvements and public housing.

Perhaps the biggest surprise on Barry's list of cuts was the deletion of $3.7 million in "site improvements" for Capitol Gateway. Capitol Gateway is an ambitious project in which the District has formed a partnership with a private developer to turn the rundown 50-acre neighborhood between South Capitol Street and the Washington Navy Yard into a $400 million complex of housing, offices and hotels.

Congress already has authorized the District to spend more than $11 million for road, sewer and water improvements for Capitol Gateway, and work had been expected to start in the coming year. A spokesman for the private developer who is to do the construction work, a subsidiary of the Dravo Corp. of Pittsburgh, and she had not been informed of the decision to delete the funds and she declined to comment on it.