(CNN) The Defense Department, under White House pressure, is expected to announce this week that billions more in Pentagon funds will go toward the border wall, according to an administration official.

A senior Defense official also told CNN that a major announcement about the border will made this week.

While the White House is poised to ask for less money for the wall in the upcoming formal budget request to Congress, the administration appears to be increasingly relying on Pentagon funds to meet its goal of constructing additional barriers on the border. The Trump administration has argued that it does not need congressional approval to redirect military funds to the border wall.

Last year, Trump declared a national emergency, allowing him to unlock billions of dollars in federal funds to mount additional barriers along the US-Mexico border. While efforts to pull from several government accounts has been met with legal challenges, the administration has pressed forward.

In January, the Pentagon received a request from the Department of Homeland Security to build and pay for hundreds of additional miles on the southwest border.

Read More