NEW YORK (AP) — New York Mayor Michael Bloomberg is leaving the nation's biggest mayoral job with a glowing view of cities' future but a stern warning that they face a serious threat: public worker pension and health care costs and the politics around them.

"It's clear that the golden age of the suburb is over, and it's being replaced by a new urban renaissance" in which cities are magnets for people and pioneers in policy, Bloomberg told The Economic Club of New York during what was envisioned as the last major speech of his 12-year tenure.

But "we cannot blind ourselves to the obstacles that stand in the way … a growing fiscal crisis that, if nothing is done, will extract a terrible toll," he said.