VATICAN CITY — Pope Francis condemned the legalization of recreational drugs as a flawed and failed experiment as he lent his voice Friday to a debate that is raging from the United States to Uruguay.

Francis told delegates attending a Rome drug enforcement conference that even limited steps to legalize recreational drugs “are not only highly questionable from a legislative standpoint, but they fail to produce the desired effects.”

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“Let me state this in the clearest terms possible,” he said. “The problem of drug use is not solved with drugs!”

“Drug addiction is an evil, and with evil there can be no yielding or compromise. To think that harm can be reduced by permitting drug addicts to use narcotics in no way resolves the problem,” he said.

Francis has years of personal experience ministering to addicts in the drug-laden slums of the Argentine capital, and he frequently has railed against drug abuse and the drug traffickers who fuel the market.

But his comments Friday marked his strongest and clearest yet as pope directed at the movement to legalize recreational marijuana, which has been gaining ground in recent years, particularly in the United States and South America.

Recreational use of marijuana has been legalized in Colorado and Washington, and Oregon may vote on the issue this year.

In Francis’ own homeland of Argentina, personal possession of controlled substances has been decriminalized. Next door in Brazil, authorities don’t punish personal drug use, although trafficking and transporting controlled substances is a crime. In December, neighboring Uruguay became the first nation to approve marijuana legalization and regulation altogether.

But Francis believes just the opposite. As archbishop of Buenos Aires, he had his priests open drug rehab centers in the Buenos Aires slums where “paco” addiction was rampant, and he famously washed the feet of recovering paco addicts during at least two Holy Thursday services. The drug is a highly addictive and cheap substance made from the by-products of cocaine and other chemicals.