CHICAGO – For cities and states buried under mountains of debt, it has become a tantalizing proposition: invite private financial institutions to put up the money to fix aging schools, dilapidated rail lines and beat-up roads. Offer investors steady returns on the projects. And give the public the modern services its governments can no longer afford.

Across the country, innovative deals are now being discussed that would put essential pieces of public infrastructure in the hands of global investment firms, the latest effort to cope with a lingering fiscal crisis that has left some communities unable to pay for their needs. Chicago, with a budget deficit of more than $600 million, is planning a private fund that would make 100 public buildings energy efficient, then move on other projects. In other parts of the country, major road construction has been funded using the model.

"We absolutely have to look at other ways" to pay for infrastructure, said Shirley Ybarra, a former Virginia transportation secretary who wrote model legislation used in 32 states for public-private transportation partnerships. "There's only so much bonding you can do ... Roads have to compete with higher education, school bonds, water and all the rest of that stuff."