Mayor Vincent Gray unveiled the plans as part of his fiscal 2014 budget proposal. (Bill O'Leary/The Post)

Mayor Vincent C. Gray is proposing to spend more than $100 million to remake the District’s four-decade-old central library, moving forward with a project that two previous mayors pondered but could not bring to fruition.

Renovating the Martin Luther King Jr. Memorial Library by 2019 would complete a 12-year, $370 million transformation of the city’s public libraries and make good on long-standing promises to revitalize the aging steel-and-glass building designed by Ludwig Mies van der Rohe.

Gray unveiled the plans as part of his fiscal 2014 budget proposal, which he presented to the D.C. Council on Thursday.

“This library has extraordinary significance,” he said during a news briefing. “This would be an effort to not only modernize the library; I think it’s a real opportunity to preserve our library.”

Gray is proposing no new taxes or fees in the new $12.1 billion budget. To pay for various new initiatives, including a 25 percent hike in the D.C. Public Library’s operating budget, Gray is relying on an anticipated $350 million rise in city revenue over the coming 18 months. Administration officials said they also expect to realize more than $50 million in savings thanks to a declining number of children in foster care, fewer special-education students being placed in private schools and tighter reins on city health-care programs.

Besides the central library project, Gray would restore seven-day-a-week operations at all neighborhood libraries for the first time since 2009, when a budget crunch led to Sunday closings and abbreviated hours at branches.

“I don’t think D.C. public libraries have ever had hours as good as we will have now,” Chief Librarian Ginnie Cooper said. “It’s very possible we’ll have better library hours than any other urban library in the country.”

City officials who briefed reporters on the central library revitalization proposal Wednesday said the funding would be used to pursue a “public-private partnership” that would likely involve sharing the historically protected building with a paying tenant.

The D.C. Public Library board commissioned designs last year that involved adding two floors to the building at Ninth and G streets NW, and making its stark interior more inviting — plans estimated to cost as much as $200 million to implement.

The $103 million that Gray is proposing would be supplemented with financing generated by the private use of a portion of the building, officials said. The bulk of the money is not scheduled to be spent until 2016, but Gray has set aside $3 million for the coming fiscal year to hire an architect and business consultants to generate a workable plan.

Cooper said one option under consideration is to lease the building to a private developer who could add as many as six stories to the building, then lease back the library space to the city. But other options will be explored, she said.

“There are a couple things we do know: We know the library will stay in this location, and we know this landmarked building will be preserved,” Cooper said. “This money means there is a commitment, finally, to have a updated, modern, wonderful central library for the nation’s capital.”

Among other budget proposals, Gray detailed how he plans to spend a promised $100 million on affordable housing programs.

The vast majority — $86.9 million through September 2014 — would be deposited in the city’s Affordable Housing Trust Fund, used to leverage financing for affordable units in private developers’ projects. Smaller amounts would fund rental housing vouchers, emergency rent assistance, home-buyer assistance and other programs.

Gray also proposes to spend an additional $1.5 million in the next 18 months on programs for homeless families and youth. The city’s family shelter has been at capacity for months, and some nonprofit groups serving homeless youth have complained about having their funding cut recently.

Major capital projects include continued funding of $400 million though 2019 for the city’s planned streetcar system — enough to complete a line running from Georgetown to the Minnesota Avenue Metro station, and to do preliminary work on a line through the Anacostia neighborhood.

A smaller-bore proposal, however, could have the most direct impact on neighborhood residents: The public works department is hoping to embark on the wholesale replacement of trash and recycling cans over the next five years. Gray is also planning to eliminate fees — currently as much as $62.50 apiece — for the replacement of lost or stolen cans.

Meanwhile, about $56 million would be set aside for city employee raises under Gray’s plan, subject to collective bargaining agreements. Separately, Gray has pledged sufficient funding to maintain the city’s police force at 4,000 sworn officers by October 2014.

Gray proposes to repeal the council’s 2011 decision to levy personal income tax on the proceeds of municipal bonds not issued in the District, a policy that was particularly unpopular among retirees. But he is not proposing to cut any other major taxes despite a near-record surplus in the last fiscal year.

Aides suggested Wednesday that the administration had not heard a strong community outcry for tax relief; Gray, in comments Thursday, said he would wait to see the findings of the Tax Revision Commission he appointed last year. “I don’t want to get out in front of them,” he said.

Over the next six weeks, the D.C. Council will evaluate and, in some cases, modify the mayoral proposal, likely taking a final vote in early June. Council Chairman Phil Mendelson (D) said Thursday that Gray’s proposal is a good start, but he “would like to see more tax relief.”