PITTSBURGH — Proposed state cuts to social service budgets could result in an additional 200 homeless people on the streets of Philadelphia, Mayor Nutter said here Thursday.

Seeking to head off that consequence, Nutter joined Allegheny County Executive Rich Fitzgerald and Pittsburgh Mayor Luke Ravenstahl in a push to encourage legislators to make changes in the $27.1 billion state budget proposed by Gov. Corbett.

Planned reductions in state contributions toward human services, economic development, and transportation programs would blow holes in their budgets, the three elected leaders said during a joint news conference. The result would harm the quality of life in Pennsylvania's two most populous counties, they said.

"We cannot balance the commonwealth's budget on the backs of the most vulnerable people," Nutter said.

The Legislature is required to approve the 2012-13 spending plan by June 30. A spokeswoman for Corbett has said that local governments must learn to live within their means.

The two mayors and county executive are Democrats, while the governor and the majority of the state Legislature are Republicans who have pledged not to impose new taxes or raise existing ones.