In a wide-ranging request for documents and analysis, President-elect Donald Trump's transition team asked the Department of Homeland Security last month to assess all assets available for border wall and barrier construction.

The team also asked about the department's capacity for expanding immigrant detention and about an aerial surveillance program that was scaled back by the Obama administration but remains popular with immigration hardliners.

The requests were made in a Dec. 5 meeting between Trump's transition team and Department of Homeland Security officials, according to an internal agency memo reviewed by Reuters.

In response to the transition team request, U.S. Customs and Border Protection staffers identified more than 400 miles along the U.S.-Mexico border, and about the same distance along the U.S.-Canada border, where new fencing could be erected, according to a document seen by Reuters.

One program the transition team asked about, according to the email summary, was Operation Phalanx, an aerial surveillance program that authorizes 1,200 Army National Guard airmen to monitor the southern border for drug trafficking and illegal migration.

The transition team also asked for copies of every executive order and directive sent to immigration agents since Obama took office in 2009.