SAN ANTONIO — Homeland Security Deputy Secretary Elaine Duke said Wednesday that environmental laws and real property acquisition are the some of the biggest obstacles the government is facing when it comes to building President Trump's wall on the southwest border, despite the constant battles in Congress over funding.

"We are not seeking to trample environmental laws, but when we lay out the timeline of building the border, I know it’s easy to focus on procurement but the real property acquisition and the environmental are the long poles in the tent, especially the real property acquisition," Duke told hundreds of border agents and immigration officers here at the Border Security Expo.

The federal process for gaining approval for building on land is "way more complicated" than state and local processes. The federal government must go through court instead of negotiating directly with local officials.

"We’re looking at that and figuring out what is the best model. I think that it’s going to depend on the space and you will see waivers where it’s necessary," she said. "What we’re looking at is, trying to be considerate and compassionate to those that are affected. There’s landowners that have land between a proposed wall, and really considering the balancing the urgency of the mission's need with the need of the people and the environment."

Last week, the department announced it would waive more than 30 environmental rules as a means of speeding up the building of border wall near the Santa Teresa Land Port of Entry in New Mexico.

Duke also said she does not expect any of the eight border wall prototypes that were constructed last fall in San Diego to be picked as the only model for construction.

"There will be variations of the physical wall. It’s not one type of wall. All the people in Border Patrol know that topography and geography and one type of wall is not going to do it," she added.

As part of DHS' strategy for securing the southwest border, roads and other infrastructure will be factored into construction plans.