NEW YORK — No one under 21 would be able to buy cigarettes in New York City, under a new proposal announced today that marks the latest in a decade of moves to crack down on smoking in the nation's largest city.

New York City Council Speaker Christine Quinn discussed details of a proposed law that would raise the minimum age for tobacco purchases from 18 to 21. City Health Commissioner Dr. Thomas Farley, some of Quinn's fellow city council members and health advocates were to join her.

Under federal law, no one under 18 can buy tobacco anywhere in the country, but some states and localities have raised it to 19. Texas lawmakers recently tried to increase the minimum age to 21, but the plan stalled.

Public health advocates say a higher minimum age discourages, or at least delays, young people from starting smoking and thereby limits their health risks. But opponents of such measures have said 18-year-olds, legally considered adults, should be able to make their own decisions about whether or not to smoke.

Some communities, including Needham, Mass., have raised the minimum age to 21, but New York would be the biggest city to do so.