Editor's Note: This story has been edited to reflect recent developments.
Donald Trump is 15 days away from starting his presidency and is already laying the groundwork for one of his biggest campaign promises: building a wall along the U.S.-Mexico border.
Reuters reports that on Dec. 5, Trump's transition team met with Department of Homeland security officials, where they talked about the assets currently available to construct the barrier.
According to a document accessed by the news wire, U.S. Customs and Border Protection staffers identified about 400 miles along the southern border where new fencing could be built.
Also, despite earlier promises, Trump said that Mexico will not be paying to construct the wall, at least not at first.
CNN reported Thursday that the Trump administration would seek taxpayer funding for the border wall; however, on Twitter, Trump added that the money "will be paid back by Mexico later."
The dishonest media does not report that any money spent on building the Great Wall (for sake of speed), will be paid back by Mexico later!
— Donald J. Trump (@realDonaldTrump) January 6, 2017
Trump's team was also interested in expanding immigrant detention centers and revamping an aerial surveillance program that was scaled back by the Obama administration.
Under President George W. Bush, Operation Phalanx, an aerial surveillance program allowing 1,200 Army National Guard airmen to monitor the U.S.-Mexico border for drug trafficking and illegal migration, was increased to 6 thousand airman. President Barack Obama has significantly cut back on the guards, a move conservatives have criticized and Trump aims to reverse.
The president-elect's transition team also asked for copies of all of the executive orders and directives Obama sent to immigration agents since 2009, a move one Department of Homeland Security official, speaking on condition of anonymity, believes was made to ensure that federal workers are not tampering with information to protect DACA recipients from deportation.
While on the campaign trail, Trump said that he would undo DACA, which allowed children brought to the U.S. illegally to remain in the country on temporary authorizations that also allowed them to work and go to college.