President Donald Trump said he plans to deploy U.S. military forces to protect the nation's southern border with Mexico while the border wall is being constructed.

"Until we can have a wall and proper security we're going to be guarding our border with the military. That's a big step," Trump said Tuesday at the White House.

"We are going to be doing things militarily," Trump added, saying that he discussed the idea with Defense Secretary James Mattis.

The Pentagon did not immediately respond to CNBC's request for comment.

While it is unclear which service branch would guard the border, the U.S. Northern Command has an area of responsibility that includes the continental U.S., Alaska, Canada, Mexico and portions of the Caribbean.