On Tuesday, President Donald Trump announced that he has begun the process of designating Mexican drug cartels as terrorist groups.

In a conversation with conservative commentator Bill O’Reilly, the media figure asked Trump whether he was going to heed suggestions from his supporters to classify southern drug cartels as terrorists following the murder of a Mormon family with dual U.S.-Mexico citizenship by gangs in Northern Mexico this month.

“They will be designated,” the president responded, according to BBC. “I have been working on that for the last 90 days. You know, designation is not that easy, you have to go through a process, and we are well into that process.”

Earlier this month, Trump promised to “wage war on the drug cartels” following the November 4 ambush that led to the death of three women and six children. The victims’ Mormon community, the LeBarons, has since petitioned the White House to list the cartels as terrorist groups.

“They are terrorists and it’s time to acknowledge it,” they wrote, with Trump supporters echoing the calls.

By designating a group as a terrorist, the U.S. makes it illegal for people to knowingly work with and support them. For instance, if gun shops or factories in the U.S. buy from Mexican cartels, as a U.S. government study found that many do, they would face severe penalties. Additionally, if there are members of the group currently in the U.S., they also risk deportation.

The designation as a terror group would also allow the U.S. to directly act against the threat. When O’Reilly asked the president if he was ready to “start hitting them with drones,” Trump said: “I’ve already offered [the Mexican president] to let us go in and clean it out and he so far has rejected the offer, but at some point something has to be done.”

While Mexican President Andrés Manuel López Obrador has expressed interest in speaking and cooperating with the U.S., he said he would not tolerate “intervention.”

“Cooperation, yes, intervention, no,” AMLO said, according to Reuters.

Foreign Minister Marcelo Ebrard reiterated the Mexican president’s sentiments, adding that the country rejects any of the U.S.’ violations of its sovereignty.

“Mutual respect is the basis for cooperation,” Ebrard said.

In the past, Colombia’s left-wing guerrillas and right-wing paramilitaries, which both have had ties to drug trade, have been designated as terrorist groups. Currently, there are dozens of groups on the list, many of them Islamist, separatist or Marxist organizations.