House and Senate lawmakers unveiled a budget agreement Friday that provides for more than $16 billion in general treasury spending over the next two years while acknowledging the state could end up spending substantially more on as-yet unbudgeted costs such as homeless programs, college scholarships and pay raises for public workers.

The budget draft announced by House Finance Committee Chairwoman Sylvia Luke and Senate Ways and Means Committee Chairman Donovan Dela Cruz also does not include hundreds of millions of dollars in spending on schools, roads and other state construction projects, and millions of dollars allocated each year to support nonprofit social service organizations.

When federal funds, special funds and other sources of revenue are figured in, House Bill 2 would authorize more than $15.36 billion in state spending in the year that begins July 1, and nearly $15.54 billion the following year.

Luke estimates there is still $100 million to $150 million in proposed programs or other initiatives that are not included in the budget, and those items will be considered in separate bills in the month ahead. That includes items such as funding for programs to cope with homelessness and a $60 million disaster relief package for Hawaii island.

The budget lawmakers offered up Friday also does not include Gov. David Ige’s initiatives to spend more than $3 million over two years to open more state-funded preschools in unused public school classrooms and to provide $19 million a year to expand “Hawaii Promise” scholarships for students in four-year University of Hawaii programs.

All of the state’s public-­worker unions are negotiating for new contracts this year, and that money also isn’t included. Each negotiated pay increase of 1 percent costs the state about $60 million in wages and fringe benefits, Luke said.

Luke said lawmakers still need to figure out how much money is available for those budget add-ons and other initiatives. She said lawmakers are considering a number of measures that might provide some extra funding.

The largest chunk of potential new revenue could come from a bill lawmakers are considering to require online vacation rental platforms such as Airbnb to collect state taxes on the rentals booked through those platforms. Lawmakers have struggled for several years to find a way to collect taxes from transient vacation rental operators in a manner that is acceptable to Ige.

Luke estimated Senate Bill 1292, if passed, would bring in an extra $45 million to $50 million a year over the next two years.

Lawmakers are also considering Senate Bill 714, which would impose state taxes on “resort fees” hotels charge their guests that are separate from basic room rates. If passed, it is expected to raise about $10 million extra per year.

Lawmakers said the budget assumes state tax collections will grow by 3 percent this year and 4 percent next year and the following year.