The Department of Homeland Security has asked the Pentagon for more help to secure the U.S.-Mexico border, while acting Defense Secretary Patrick Shanahan says he is prepared to keep American troops in the region longer-term to enact President Donald Trump’s hard-line immigration plans.

DHS has asked the Defense Department to help provide more housing for migrants who are being detained along the border, defense officials confirmed to multipleoutlets this weekend. That housing would include more tents, which U.S. Customs and Border Protection has been building at breakneck pace to try and keep up with the tide of people being arrested daily.

Despite that effort, the U.S. Border Patrol has been struggling to house and process up to 5,500 people per day who attempt to cross into the country, and more than 17,500 are being held in cells and tents along the border. The Washington Post reported that detention facilities are so full in some places, the U.S. has been flying migrants from one spot on the border to another just to process them.

Shanahan visited the border this weekend alongside acting DHS chief Kevin McAleenan to voice his support for Trump’s renewed effort to quash undocumented immigration. The president recently cleared out many top immigration officials, including former DHS Secretary Kirstjen Nielsen, and replaced them with officials Trump believes will better implement his restrictive approach.

“We’re not going to leave until the border is secure,” Shanahan said in McAllen, Texas, according to The Associated Press. “This isn’t about identifying a problem. It’s about fixing a problem more quickly.”

He said that while the Pentagon wouldn’t pull troops from the region prematurely, he hoped to help Customs and Border Protection set up enough infrastructure to continue on its own. The AP notes that nearly 4,400 military troops are currently on the southern border, helping erect fencing and other infrastructure and providing logistical support to CBP.

“What we want is for DHS to be effective and stand alone,” Shanahan said.

The acting Pentagon chief drew the ire of many Democrats this week after he said the Defense Department would move $1.5 billion in funding from various military programs to help build Trump’s long-promised border wall. Some lawmakers say such an effort runs afoul of congressional authority.