AUSTIN, Texas — The head of the U.S. Border Patrol is frustrated that his federal law enforcement agents have been pulled from their posts guarding against drugs like fentanyl and dangerous criminals to process the tens of thousands of immigrants who poured across the border last week.

Border Patrol Chief Jason Owens said it is not the job of the 19,000 Border Patrol agents nationwide to intake immigrants who cross the border illegally, but that organized crime groups in Mexico have done so to keep agents out of the field.

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"I believe it's a money-making opportunity for those smugglers, and I believe it’s a distraction to cross other things into the country ... narcotics, fentanyl, bulk cash, weapons, people of interest, whether it be hardened criminals, gang members, convicted sexual predators," Owens told ABC News's This Week in an interview that aired Monday.

Mexican cartels have not only taken advantage of Border Patrol being distracted but instigated the distraction in the first place, Owens explained. Pulling agents from the field leaves vast, open spaces for cartels to move criminals, bulk cash, weapons, and drugs across the border undetected.

Across the 2,000-mile southern border, certain regions have been hit harder than others in terms of illegal immigration. Arizona's Tucson region, as well as El Paso, Eagle Pass and Del Rio, and the Rio Grande Valley of Texas, have seen staggering increases in the number of immigrants apprehended after crossing illegally.

Particularly in Eagle Pass, a remote town in south-central Texas, Border Patrol was so overwhelmed by the thousands that streamed across the Rio Grande each day that overflow rooms were packed, and thousands of people were held for periods outside under an international bridge while waiting to be transported to federal facilities.

"In terms of flow and the threats that we're seeing with fentanyl and with criminal organizations that are our adversary, it’s about as bad as I've ever seen," Owens said. "A lot of times our facilities are already over capacity."

One day last week, the Eagle Pass/Del Rio region had more than 3,000 people in custody, with only room to detain 1,800 people. Border Patrol cannot continue to respond to this level of people attempting to cross illegally, according to the chief.

"This isn't sustainable. This is up and down — the system — everybody is overwhelmed, even the government of Mexico, which has been great partners for us, the U.S. Border Patrol," Owens said.

Despite the dire circumstances, Owens said agents cannot deter or turn away immigrants.

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"We see a lot of — a lot of folks say, 'Just push people back. Just don't let them cross or send them back immediately,'" Owens said. "The U.S. Border Patrol is a law enforcement agency. We enforce the laws that are on the books. We don't have the right — nor should we have — denying somebody due process once they are on U.S. soil."

President Joe Biden is scheduled to travel to Arizona later this week, but the White House has not indicated if he will visit the southern border during his trip.