New York City plans to enact a far-reaching ban on the sale of large sodas and other sugary drinks at restaurants, movie theaters and street carts, in the most ambitious effort yet by the Bloomberg administration to combat rising obesity.

The proposed ban would affect virtually the entire menu of popular sugary drinks found in delis, fast-food franchises and even sports arenas, from energy drinks to pre-sweetened iced teas. The sale of any cup or bottle of sweetened drink larger than 16 fluid ounces — about the size of a medium coffee, and smaller than a common soda bottle — would be prohibited under the first-in-the-nation plan, which could take effect as soon as next March.

The measure would not apply to diet sodas, fruit juices, dairy-based drinks like milkshakes, or alcoholic beverages; it would not extend to beverages sold in grocery stores or convenience stores.

“Obesity is a nationwide problem, and all over the United States, public health officials are wringing their hands saying, ‘Oh, this is terrible,’ ” Mr. Bloomberg said in an interview on Wednesday in City Hall’s sprawling Governor’s Room.