The new chairman of the House Armed Services Committee on Sunday said President Trump Donald John TrumpBarr criticizes DOJ in speech declaring all agency power 'is invested in the attorney general' Military leaders asked about using heat ray on protesters outside White House: report Powell warns failure to reach COVID-19 deal could 'scar and damage' economy MORE "doesn't really understand" border security as Trump continues to demand that a wall be built along the border with Mexico.

Rep. Adam Smith David (Adam) Adam SmithWhen 'Buy American' and common sense collide Overnight Defense: Marine Corps brushes off criticism of Marines' appearance in GOP convention video | US troops injured in collision with Russian vehicle in Syria | Dems ask for probe of Vindman retaliation allegations Democrats press Pentagon watchdog to probe allegations of retaliation against Vindman brothers MORE (D-Wash.) also said during an appearance on ABC's "This Week" that there is "no evidence whatsoever" that the southern border needs a wall, adding that portions of the border already have one.

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"The president doesn't really understand the issue," he said. "A concrete barrier is not going to automatically stop people from coming."

“The wall is not in itself a bad idea," Smith added. "It’s just that it’s been done. And what the president has not done is he has not made the case that on the portions of the border where a wall has not been built, how is a wall going to enhance border security? There is no evidence whatsoever that that’s necessary.”

The federal government is currently in its third week of a partial shutdown that was sparked because of Trump's demand for $5 billion in funding for the border wall. Lawmakers have been at odds over that demand, with Democrats pledging not to fund a wall.

Smith on Sunday also dismissed the notion that Trump should declare a national emergency to build the wall, something the president has threatened to do.

Smith said that the "short answer" is that Trump has the authority to declare an emergency, but added that it would be a "terrible" decision and said Trump would immediately face legal challenges.

“There is a provision in law that says the president can declare an emergency. It’s been done a number of times. But primarily it’s been done to build facilities in Afghanistan and Iraq. And in this case I think the president would be wide open to a court challenge saying, ‘Where’s the emergency?’ You have to establish that in order to do this," Smith said.

“But beyond that, this would be a terrible use of Department of Defense dollars," he continued. "The president spends most of his time talking about how we’re not spending enough on national security. Now he wants to take $20 billion dollars out of the defense budget to build a wall, which by the way is not going to improve our border security.”