Sen. Bernie Sanders said Wednesday although he believes border security is "enormously important," building a wall would be the wrong way to improve it.

Sanders (I-Vt.) said on Special Report that President Trump's border wall would be "costly and ineffective," and that he's not alone in that opinion.

"Many experts think that given the kind of technology that we have today, we can protect our southern border without building the wall and spending $5 billion," he said.

He added that he's unsure if Trump has enough House votes to, in fact, construct the wall.

Bret Baier responded by noting that in 2013, Sanders voted for comprehensive immigration reform, which included several billion dollars for a wall and enhanced security.

"So you're saying that the $5 billion is a non-starter?" he asked.

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Sanders said that the $5 billion in border wall funds would be part of tens of billions more that would be allocated toward a wall.

"Sometimes you vote for things that are part of a broad package," the senator said. "But if you're asking me ... [if] it's a good investment for the taxpayers of this country to build a wall, no, I don't think it's a good investment."

Sanders also commented on a Senate resolution that he is co-sponsoring, that aims to punish Saudi Arabia for the killing of activist Jamal Khashoggi.

The measure would pull U.S. support for troops fighting in Yemen's civil war, but most Republicans reportedly oppose it. 

Sanders called the crisis in Yemen the "worst humanitarian disaster" facing the planet.

"The Congress of the United States has abdicated its constitutional responsibility over war-making," he said. "It's not the president who has the responsibility under the Constitution to send our troops off to war, it is Congress, and we have to got to take it back.

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