Mayor Bill de Blasio is championing a plan that would make New York City a pioneer in creating supervised injection sites for illegal drug users, part of a novel but contentious strategy to combat the epidemic of fatal overdoses caused by the use of heroin and other opioids.

Safe injection sites have been considered successful in cities in Canada and Europe, but do not yet exist in the United States. Leaders in San Francisco, Philadelphia and Seattle have declared their intention to create supervised sites, although none have yet done so because of daunting obstacles. Among them: The sites would seem to violate federal law.

The endorsement of the strategy by New York, the largest city in the country, which last year saw 1,441 overdose deaths, may give the movement behind it impetus.

For the sites to open, New York City must still clear some significant hurdles. At minimum, the plan calls for the support of several district attorneys, and, more critically, the State Department of Health, which answers to Gov. Andrew M. Cuomo. The city sent a letter on Thursday to the state, asserting its intention to open four injection centers.