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As the opioid epidemic continues to rage across the nation, the city of Philadelphia plans to experiment with an overdose prevention strategy never before tested in the U.S.

On Tuesday, officials in Philadelphia announced their support for so-called “safe injection sites” — medically supervised locations where users can inject heroin and other opioids without fear of arrest.

The walk-in sites would offer sterile needles and naloxone, an overdose-reversing drug. In addition to medical supervision, users would have access to treatment information.

The city expects injection sites to prevent between 24 and 76 opioid overdose deaths each year, as well as between one and 18 cases of HIV infection.

“Extraordinary times require novel thinking,” Philadelphia’s health commissioner, Dr. Thomas Farley, told NBC News. “This is a public health crisis truly of historic proportions.”

Overdose deaths in Philadelphia are estimated to have reached 1,200 last year — about 85 percent were opioid related and the overall number was nearly four times the number of homicides. For the first time, overdose fatalities last year surpassed the 935 deaths recorded at the peak of the AIDS crisis in Philadelphia in 1994.

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City officials characterized the Tuesday announcement as an effort to solicit proposals from private groups interested in opening safe injection sites, which it refers to as Comprehensive User Engagement Sites (CUES). It would likely take months before any such site actually opened, they noted.

The initiative is the product of a task force assembled in January last year by Philadelphia Mayor Jim Kenney to combat the opioid epidemic. The task force issued a report in May with 18 recommendations, one of which was to explore safe injection sites on a pilot basis.

A heroin addict prepares to inject himself in the Kensington section of Philadelphia, which has become a hub for drug users. Spencer Platt / Getty Images

But opposition remains. “I don’t see this as a well thought-out, practical plan,” said David Oh, a city councilman and member of the task force. “I don’t know how they would possibly get past zoning. Who is going to insure liability for those private investors?”

The scourge of opioid addiction has been notably acute in Philadelphia, where fatal overdoes doubled in just four years — from 459 deaths in 2013 to 907 in 2016.

The city’s fatal overdose rate of 46.8 deaths per 100,000 residents far outpaced that of other large cities, such as Chicago (15.4) and New York (11.2) in 2015.

Related: Safe injection sites could be a way to combat the opioid epidemic

The increasing prevalence of fentanyl — a synthetic opioid up to 100 times more potent than morphine — partly explains the recent surge. Fentanyl was found in 412 drug overdose deaths in Philadelphia in 2016, a sharp increase from the nine instances recorded four years prior, according to a report prepared by city officials.

Safe injection sites have operated in Europe since the late 1980s and have been used in Canada and Australia more recently. North America’s only standalone safe injection site — known as InSite — opened in 2003 in Vancouver, British Columbia. InSite has served as a model for Philadelphia policymakers, who traveled there as part of their research.

Seattle announced that it would open two safe injection sites last year, though they are not up and running yet.

Meanwhile, the Justice Department, under the Trump administration, has urged prosecutors to pursue the maximum sentences available for drug offenses — reversing Obama-era guidance and showing signs of a stricter overall approach to drug criminalization.

Asked how Philadelphia would respond to pushback from federal authorities, Farley said he was “hopeful that the federal government will not interfere with local governments trying to save lives.”

At a press conference on Tuesday, Philadelphia Police Commissioner Richard Ross said his attitude about safe injection sites evolved from staunch opposition to “having an open mind.”

“There’s a lot of lives being lost," he said, "and that is something that, in the world of public safety, we certainly cannot just throw up our hands up and say, ‘That’s not my problem.'"