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. And it asked whether federal workers have altered biographic information kept by the department about immigrants out of concern for their civil liberties.

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. The document offers a glimpse into the president-elect's strategy for securing the U.S. borders and reversing polices put in place by the Obama administration. 

Trump's transition team did not comment in response to Reuters inquiries. A spokeswoman for the Department of Homeland Security and U.S. Customs and Border Protection declined to comment. 

    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.