NEW YORK — Mayor Michael Bloomberg signed landmark legislation Tuesday banning the sale of tobacco products to anyone under the age of 21, making New York the first large city or state in the country to prohibit sales to young adults.

During a brief ceremony at City Hall, Bloomberg said raising the legal purchase age from 18 to 21 will help prevent young people from experimenting with tobacco at the age when they are most likely to become addicted. City health officials say 80 percent of smokers start before age 21.

The mayor, a former smoker, also signed legislation setting a minimum price for all cigarettes sold in the city: $10.50 per pack. The same new law bans retailers from offering coupons, 2-for-1 specials, or other discounts.

In signing the bills, Bloomberg turned away criticism that the measures would be economically harmful to thousands of city convenience stores and possibly lead to job losses.

“This is an issue of whether we are going to kill people,” Bloomberg said. People who raise the economic argument, he said, “really ought to look in the mirror and be ashamed.”

The ban does have limitations. People under age 21 can still possess tobacco legally, they just can’t buy it. Underage smokers will still be able to steal cigarettes from their parents, bum them from friends, stock up during trips beyond city limits or buy them from the black-market dealers common in many neighborhoods.

Young smokers puffing away outside the main library at New York University on Tuesday ridiculed the law as an infringement on personal freedoms and questioned whether it would really lead to reduced smoking rates.

“I think Bloomberg has just exponentially increased the fake ID industry in New York,” said Jakob Sacksofsky-Bereck, age 19.

“It’s obviously going to make life more complicated, said fellow student Josh Kundert-Gibbs, also 19. “We are going to have to buy in bulk.”

Both said, though, that they regretted ever having started smoking in the first place.

City Health Commissioner Thomas Farley said the idea is to make it more inconvenient for young people to start smoking regularly, especially young teens who now have easy access to cigarettes through slightly older peers.

“Right now, an 18-year-old can buy for a 16-year-old,” he said. Once the law takes effect, in 180 days, Farley said, that 16-year-old would “have to find someone in college or out in the workforce.”

The city estimated that there are 27,000 New Yorkers ages 18 to 20 who smoke.

Tobacco companies and some retailers had opposed the age increase, saying it would simply drive people to the city’s thriving black market.

“What are you really accomplishing? It’s not like they are going to quit smoking. Why? Because there are so many other places they can buy cigarettes,” said Jim Calvin, president of the New York Association of Convenience Stores. “Every 18-year-old who walks out of a convenience store is just going to go to the guy in the white van on the corner.”

Large cigarette companies now commonly offer merchants incentives to run price promotions to bring in new customers. Those discounts, though, will be banned by the new law, which aims to keep the price of cigarettes high as a way of deterring smokers. The city already has the nation’s highest cigarette taxes.

Calvin said the elimination of discounts would further feed the drift away from legal cigarettes, and toward illicit supplies brought into the city by dealers who buy them at greatly reduced prices in other states, where tobacco taxes are low.

Both bills were passed by the City Council late last month. The legislation also prohibits the sale of small cigars in packages of less than 20 and increases penalties for retailers that violate sales regulations.

– WALL STREET JOURNAL