U.S. Surgeon General Jerome M. Adams, in Philadelphia on Saturday to participate in a march to combat stigma against drug addiction, said the Trump administration has made its position on safe injection sites clear: Despite the city's efforts to sanction a site where people can use drugs under medical supervision in order to prevent overdoses, federal officials believe the measure is a violation of federal law.

Instead, Adams said, the federal government should spend its energy working to expand other harm-reduction measures that have been endorsed by the feds, like needle exchanges, which have been shown to reduce the spread of blood-borne infections like HIV and hepatitis C.

"I was reading in the newspaper that Philly has only one syringe service program," Adams said. "I think there's a lot we can do to optimize evidence-based solutions that are already out there and available."

>> READ MORE: Safe injection sites get green light from Philadelphia officials

(Needle exchanges themselves are still controversial in some circles: They remain illegal in Pennsylvania, and only a handful of cities around the state have established needle exchanges, usually with the permission of a local district attorney or mayor. When Mayor Ed Rendell signed an executive order to open Philadelphia's only needle exchange, Prevention Point, in the early 1990s, state officials threatened staffers with arrest.)

Safe injection sites have been in place in countries like Canada and Germany for decades. A study commissioned by city officials earlier this year estimated a single site in Philadelphia would save 25 to 75 lives a year and millions of dollars in hospital costs and public funds, while reducing public injection of drugs and other neighborhood problems in a city where 1,217 people died of an overdose last year.

It's the highest death rate in any major city in the country.

Still, in an interview last month with WHYY, Deputy Attorney General Rod Rosenstein said the city should expect legal action if it tries to open a site. (It's unclear whether that would mean civil or criminal action, and local legal experts have said the city can argue that safe injection sites are a lifesaving measure amid an opioid crisis that has resisted traditional attempts to curb overdose deaths.)

Adams, whose brother suffers from opioid addiction, said he chose to march in Philadelphia on Saturday — alongside thousands of others — because of the unique toll the opioid crisis has taken on the city. The PRO-ACT Philadelphia Recovery Walk, held annually since 2001 and supported through the city's Department of Behavioral Health and Intellectual disAbility Services, is believed to be the largest addiction recovery walk in the country, drawing 27,000 participants last year.

"There's nowhere where things are as bad or where there's as much hope as in Philadelphia," Adams said. He said he wanted to show that recovery from addiction is possible and that the federal government needs to work to increase access to treatment and dispel stigma.

And he praised housing-first programs in Philadelphia that offer people with addiction homes with no requirement for sobriety.

"Housing is health," he said. "The opioid epidemic is a tragedy, but it's also an opportunity for us to help folks understand that health is about housing, it's about jobs, it's about everything that's going on in your community and your environment. If we don't create healthy and well communities, we're just going to play whack-a-mole."