Defense Secretary Jim Mattis has discussed with President Trump the idea of building a southern border wall using funds from the defense budget, but that’s all the Pentagon is saying about it.

At the Pentagon’s regular Thursday briefing, chief spokesperson Dana White said the idea has come up in conversation between the two men, but gave no details on what Mattis told Trump.

“What I can tell you is that the secretary has talked to the president about it, but I don't have any specifics,” White said.

“The president and the secretary talk frequently … about a variety of subjects. This was one of them. And I don't have any more details for you.”

Privately, Pentagon officials say any reprogramming of funds seems unlikely given that it requires congressional approval.

Pressed about whether Mattis advised the president that diverting money for the border wall could undermine the secretary’s priority to improve the lethality of the military, White said, “There's no daylight between them with respect to ensuring that this military stays most lethal in the world. There is no disagreement between them on that issue."

On Sunday, Trump tweeted that "our Military is again rich," and that the U.S. should "Build WALL through M!" The Washington Post later reported that Trump that "M" stood for military.

