Attorney General Jeff Sessions on Wednesday gave his strongest signal yet that the Justice Department's more hands-off approach to marijuana enforcement may soon be changing.

Sessions said that the department is looking "very hard right now" at a directive carried over from the Obama administration that effectively encourages federal prosecutors to generally defer to state laws that legalize marijuana use.

"We had meetings yesterday and talked about it at some length," the attorney general said, speaking at a press conference on new measures to combat opioid abuse. "It's my view that the use of marijuana is detrimental, and we should not give encouragement in any way to it, and it represents a federal violation, which is in the law and it's subject to being enforced, and our priorities will have to be focused on all the things and challenges we face."

He added: "We'll be working our way through to a rational policy. But I don't want to suggest in any way that this department believes that marijuana is harmless and people should not avoid it."

Sessions, a former Republican senator from Alabama who built a reputation on Capitol Hill as a supporter of traditional law-and-order policies, has long been a vocal opponent of legalizing marijuana.

He has been critical of the so-called "Cole memo" from 2013, authored by Deputy Attorney General James Cole, which told Justice Department attorneys that marijuana use in "jurisdictions that have enacted laws legalizing marijuana in some form … is less likely to threaten federal priorities."

As attorney general, he has roundly dismissed research that has linked the use of medical marijuana to reductions in opioid-related deaths. In May, he explicitly asked Congress in a letter to undo a 2014 amendment that has protected medical marijuana providers.

"I am astonished to hear people suggest that we can solve our heroin crisis by legalizing marijuana – so people can trade one life-wrecking dependency for another that's only slightly less awful," Sessions said in March during a speech in Richmond, Virginia.

Since April, a task force at the Justice Department has been reviewing the Cole memo and the department's approach to marijuana enforcement. Documents obtained by the Associated Press this summer indicated that the task force recommended largely keeping the Cole memo in place.