(CNN) The Department of Homeland Security will ask the Pentagon this week to approve plans to potentially house more than 7,000 unaccompanied children at Goodfellow Air Force Base in Texas and 4,000 additional migrant family members at Fort Bliss, according to an administration official.

The official emphasized that these are planning numbers, and it's not clear those numbers of people will need to be housed.

Defense Secretary James Mattis, who must sign off on the plan, confirmed the proposal but would not offer any specifics. He said the military is not involved in the political aspects of the matter: "For us, it is a logistics support effort."

Once Mattis approves the DHS plan, the Pentagon will hire contractors to build temporary structures. Bliss is expected to be all tents, while Goodfellow may have a combination of tents and hardened structures.

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