U.S. Attorney General Jeff Sessions said on Thursday that the first step to combating the country's opioid crisis is to get people to just "say no" to drugs, and he warned that marijuana could be serving as a gateway to the problem.

"We've got to re-establish first the view that you should say no. People should say no to drug use. They have got to protect themselves first," he said, during a question-and-answer session at the Heritage Foundation think tank in Washington.

He added that "fentanyl people are really killers," but did not clarify to whom he was specifically referring, and said he has heard from many police chiefs that drug addiction "starts with marijuana."

(Reporting by Sarah N. Lynch; Editing by Jonathan Oatis)