Washington (CNN) President Donald Trump has privately floated the idea of funding construction of a border wall with Mexico through the US military budget in conversations with advisers, two sources confirmed to CNN Tuesday.

Trump discussed the idea in a private meeting last week with House Speaker Paul Ryan, a source familiar with the conversations said, as he reviewed the omnibus spending bill, which does not include funding for construction of a border wall. It was not immediately clear how serious Trump was about pursuing this option, but the move would likely face steep hurdles with appropriators in Congress.

The idea is Trump's latest attempt to find a way to build the border wall he promised supporters during his campaign as Mexico has dismissed his call for Mexico to fund its construction. Trump has said he would seek that payment in the form of a refund, either through trade negotiations, remittance payments or other means.

Congressional budgeting is done with very specific instructions for how dollar amounts are spent. Any repurposing of funds requires express congressional approval, which Trump is unlikely to get. The source noted that additional authorization from Congress would likely be necessary if this option was pursued.

A senior administration official confirmed the President has floated this idea, along with others, as alternative ways to pay for the wall.

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