Gov. Jerry Brown and Democratic leaders in the Senate and Assembly have reached a deal on a $4 billion bond measure to fund affordable housing in the state.

The measure addresses one cause of California's affordable housing crisis: a lack of state funding to construct homes for low-income residents.

Senate Bill 3, authored by Sen. Jim Beall of San Jose, originally proposed $3 billion to fund the construction of new housing. The deal announced late Monday adds $1 billion to that total for the Cal-Vet Loan Program, an initiative to provide home loans to California veterans that expires next year.

“The bond agreement we have reached provides badly needed funding to help Californians, including our veterans, find safe, affordable housing," said Assembly Speaker Anthony Rendon, D-Lakewood, in a statement. "We’ve said before: It shouldn’t cost an arm and a leg to put a roof over your head -- and this agreement will make housing more affordable for many Californians."

The original bond proposal has faced criticism for not being large enough to chip away at the state's affordable housing shortage.

The Legislative Analyst's Office estimated that the state would need to spend $15 billion to $30 billion annually in bonds or subsidies to provide enough housing for Californian's lower-income households.

State Treasurer John Chiang, a 2018 gubernatorial candidate, has called on lawmakers to increase the bond size to between $6 billion and $9 billion.

A bond of that magnitude could threaten the bipartisan support that Senate Bill 3, which needs to be approved on a two-thirds vote in both houses, enjoyed in the state Senate.

On Monday, Beall made a late pitch for the bond, which he says will generate 137,000 jobs.

"It will only get worse if we don’t do this," he said. "This is a sense of urgency that we now have in California to produce more affordable housing."

Democratic leaders could announce further agreement on housing legislation, including bills to create new housing revenue and change local rules around housing approval, as early as Tuesday.