A Department of Defense spokesperson confirmed that the Department of Homeland Security made the request, and a Defense official said acting Secretary Patrick Shanahan is expected to sign the request.

The tents will probably not be on military bases, and Immigration and Customs Enforcement — not the military — will be responsible for migrant detention and custodial support.

In a statement, a Defense Department spokesman said that DHS made the "Request for Assistance (RFA)" on May 9.

"After discussions with DHS on the details of the RFA, DHS has agreed to ask that DOD will loan and erect on-hand DOD tents in support of ICE, and provide contracting support to ICE for wraparound services for which ICE will reimburse DOD," Maj. Chris Mitchell said. "DOD will not provide detention or custodial support for detained aliens at these ICE detention facilities."

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The announcement came as senior administration officials confirmed that President Donald Trump will roll out a two-pronged immigration proposal Thursday that would make sweeping changes to the legal immigration system and enhance border security.

The plan, which Trump is expected to announce during an afternoon speech, avoids some of the most hot-button immigration issues of the day — including a growing backlog of asylum-seekers and the status of so-called "Dreamers" — and is almost certainly doomed on Capitol Hill.