A Border Patrol vehicle sits along the U.S.-Mexico border wall on January 25, 2017 in San Ysidro, California. Sandy Huffaker/Getty Images The Trump administration reportedly put in a formal request for $1 billion in funding for the first sections of a wall along the US-Mexico border, including replacing some southern fencing, CNN reported on Monday evening.

Documents from the Department of Homeland Security cited by CNN note that the funding would cover 48 miles of new wall construction.

According to CNN the money will pay for:

14 miles of new border wall in San Diego.

14 miles of replacement fencing in San Diego.

28 miles of new levee wall barriers in the Rio Grande Valley region.

Six miles of new border wall, also in the Rio Grande Valley region.

Trump's border wall would require billions of dollars in investment. Business Insider's Michelle Mark reported last week that the president's budget proposal includes a $2.6 billion investment on "tactical infrastructure" and designs and planning for the wall as well as $314 million toward hiring and training 500 border-patrol agents and 1,000 Immigration and Customs Enforcement officers in 2018.

The budget proposal appears to fall short of early cost estimates for the wall's construction and maintenance, which could total as much as $21.6 billion, according to a Department of Homeland Security report last month. Trump himself previously cited a cost of $12 billion for the wall.

Michelle Mark contributed to this report.