Criminal cartels are using groups of migrants as a distraction for their drug smuggling activities on the southern border, according to the commander of U.S. Northern Command.

The military has noticed a "relationship" exists between migrants and drug flows, Gen. Terrence O'Shaughnessy said during a talk the Center for Strategic and International Studies on Monday. His command is trying to help the Department of Homeland Security counter the problem.

"The same cartels that are working the drug smuggling are working the migrants and where the migrants are going," O'Shaughnessy said. "We also see them using the migrants as a distraction. And so as they push a group of migrants over here, the drug smuggling goes over there. And we see that coordinated behavior, which we are trying to help plug some of those gaps."

O'Shaughnessy said he was surprised to learn the severity of the narcotics problem when he took over as the head of NORTHCOM in May 2018. As the military command principally responsible for the defense of the U.S. homeland, NORTHCOM plays a supporting role in counternarcotics initiatives, specifically with the Drug Enforcement Administration.

"And why? It's because this is a national crisis. 70,000 Americans killed [by] overdose," O'Shaughnessy said. "How can the Department of Defense not be part of that solution set?"

O'Shaughnessy noted that NORTHCOM isn't the lead agency on the issue but does play a key role through Joint Task Force North, which focuses on aiding Customs and Border Protection in counter-narcotics operations.

The Pentagon said Wednesday that it will be sending an additional 2,100 troops and members of the Texas National Guard to assist in securing the southern border. They will join the already 4,500 troops currently stationed in the area.