NEW YORK -

New York City's billionaire mayor is using his personal fortune to try to spark innovation in the nation's cities.

The mayor tells The Associated Press that his organization, Bloomberg Philanthropies, is inviting the mayors of the nation's 1,300 largest cities to compete for five prizes totaling $9 million.

Mayors of cities larger than 30,000 people will receive letters this week asking them to submit proposals meant to solve major challenges and improve city life. The foundation is asking them to focus on initiatives that could be replicated.

Bloomberg says that U.S. mayors are faced with similar challenges and he wants to reward the creation of great ideas.

He says the competition is for mayors, not organizations, because while "organizations tend to talk a lot ... mayors don't have that option."

One grand prize of $5 million and four $1 million prizes will be awarded in May 2013.