WASHINGTON (AP) — President Donald Trump has raised the idea of using the Pentagon budget to pay for the border wall he vowed to build and make Mexico pay for it.

Departments, however, have limited authority to reprogram funds without congressional approval.

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Pentagon spokesman Chris Sherwood referred questions on the wall to the White House, where spokeswoman Sarah Huckabee Sanders said she was “not going to get into the specifics of that.”

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Last week, Trump threatened to veto the omnibus spending bill, in part because it didn’t include the $25 billion he wanted for the wall. Trump tried to justify signing the deal by pointing to the boost in military funding, but he nonetheless remains frustrated.

A GOP aide says the Senate Appropriations Committee isn’t aware of any authority that would allow the Defense Department to fund the wall without congressional approval.

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