As the government shut down drags on to its third week, the battle for a border wall continues.

President Trump is leaning more toward having a steel barrier versus the proposed concrete wall.

Trump is not giving up on his proposed border wall and offered plans of a steel barrier, which he believes makes for a more suitable solution than a concrete wall.

“It may be better, but I’m willing to do that so our great steel companies, which are now back in business. They were doing very poorly when I took office and now they’re doing very well,” Trump said on Sunday prior to his trip to Camp David.

The president tweeted Sunday that a steel barrier would be stronger, but one structural engineer said otherwise.

“Concrete is a stronger material and more durable than steel,” said George Mendoza, President of Mendoza Engineering.

In Trump’s tweet, he adds that using steel will be less intrusive.

Mendoza explains that with the current fences you can see through them, which makes it not as “menacing” looking compared to a solid wall.

Although constructing a concrete wall will take time, Mendoza says it will last longer without having to do frequent maintenance.

“Steel, since it’s exposed to the weather, it will over time exhibit rust or perhaps other problems that mother nature causes to it,” said Mendoza.

However, the engineer said using concrete material comes with a price.

“I can tell you a concrete wall will be more expensive to build,” said Mendoza. “Now in the long run it will be cheaper to maintain.”

Trump believes the border wall must be kept a priority and is still asking congress for $5.7 billion in funding.

“You think I like doing this? I don’t like doing this. But we have no choice, we have to have it,” said Trump

Trump has threatened to declare a national emergency if Congress refuses to fund the U.S.- Mexico border wall.