The Pentagon’s acting chief is visiting the U.S.-Mexico border in Texas as he considers how to use emergency powers invoked by President Donald Trump to help build a border wall.

Acting Defense Secretary Patrick Shanahan arrived Saturday in El Paso with Gen. Joseph Dunford, chairman of the Joint Chiefs of Staff.

Shanahan plans to get a firsthand view of areas along the border, west of El Paso, where military troops are assisting U.S. Customs and Border Protection with barrier replacement work. The sites are along known drug smuggling corridors.

It’s Shanahan’s first visit to the border since taking over at the Pentagon on Jan. 1 after Jim Mattis resigned as defense secretary in protest of Trump’s policies.