Congressional budgeting is done with very specific instructions for how dollar amounts are spent.
After floating the notion to several advisers last week, he told Speaker Paul D. Ryan (R-Wis.) that the military should pay for the wall in a meeting last Wednesday in the White House residence, according to three people familiar with the meeting.
The new border aims to have walls between 18-30 feet high and a 150 feet (45m) electronically monitored no-man's land between America and Mexico.
Trump has also proposed making Mexico pay for the wall indirectly through measures such as increasing visa fees, imposing new tariffs and targeting remittances.
In a tweet Tuesday, Trump argued that the military is "rich" and building a border wall is all about national defense because there are "enemy combatants pouring into our Country".
4 of 9 The president has warned there would be "bedlam" without the controversial wall he wants to build on the border with Mexico. Trump wanted as much as $25 billion for his wall project, but the legislation authorized only $1.6 billion for fencing, surveillance technology and other measures.
Trump has apparently already publicly made this declaration.
Trump's push to enlist the military in his wall-building plans are likely to be resisted by Defense Secretary Jame Mattis, who has successfully avoided most partisan disputes. Trump tweeted on Sunday, apparently referring to the US military, not Mexico. "You could always increase them and take the revenue for that for resources", the same official said, who also described these options as Trump's "musings".
The "M" stands for military, not Mexico.
The Washington Post reported that, in an infraction with senior aides last week, Trump mentioned how the Defense Department was receiving such a large budget from the spending bill (about $700 billion) and that the Pentagon would be able to fund the project.
"We can't allow Donald Trump to steal already-limited resources from our troops to fund a pointless border wall that will serve little other objective than to satisfy his own fragile ego", Rep.
The White House was asked on Tuesday if it is true that Mexico isn't going to pay for the wall.
Gallego's amendment to the National Defense Authorization Act (NDAA) past year was seen as largely symbolic since there had been no proposal to use Pentagon funding for the wall.