New York City Mayor Michael Bloomberg is hoping to encourage new mothers to breast feed their children.

"Latch on NYC," a policy set to start in September, is voluntary for hospitals. Under the program, formula bottles will remain locked up, like medicines are currently kept.

Mothers who insist on not breastfeeding or who are unable to will be allowed to bottle feed. However, nurses will have to sign out the baby formula.

Critics say Bloomberg is imposing a "nanny state."

Still, the National Alliance for Breastfeeding Advocacy said the program could have positive effects.