Eielson Air Force Base, Alaska (CNN) Defense Secretary James Mattis said the Pentagon is in "close alignment" with the Department of Homeland Security with efforts to utilize military bases to house undocumented immigrants along the southern US border.

The Department of Homeland Security has "come to us asking us to build temporary camps on two of our bases," Mattis told reporters on board his plane at the beginning of a trip that will take him to Alaska, China, South Korea and Japan.

"We are in a logistics support response mode," with DHS, Mattis said, adding that "details are still being worked out" with respect to how the Pentagon's role in the operation will play out, while likening the response to the Defense Department providing housing to Vietnamese refugees rescued at sea in the years after the Vietnam War and for victims of hurricanes and other natural disasters.

"This is something that we can do again, whether it be refugee boat people from Vietnam, people that have been knocked out of their homes by a hurricane, absolutely it's appropriate to provide logistical support however it's needed," Mattis said of his department's role in the effort.

Health and Human Services officials have toured four US military bases in Texas and Arkansas as possible locations.

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