President Trump Donald John TrumpBiden leads Trump by 36 points nationally among Latinos: poll Trump dismisses climate change role in fires, says Newsom needs to manage forest better Jimmy Kimmel hits Trump for rallies while hosting Emmy Awards MORE said during a visit to San Diego on Tuesday that he needs his proposed border wall with Mexico to be a tough physical obstacle, as those seeking to enter the U.S. illegally are "incredible climbers."

"Getting over the top is easy. These are like professional mountain climbers, they're incredible climbers. They can't climb some of these walls,” Trump told reporters during a tour of border wall prototypes.

Trump viewed eight such prototypes during his California visit and noted that a wall with “see-through capability” would be beneficial in combating cartels.

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"You have to know what's on the other side of the wall," Trump said. "You could be two feet away from a criminal cartel and don't even know they're there. Now we have equipment to take care of that, X-ray equipment, et cetera."

Trump said that the wall is “our first line of defense” and made the case that it will save “hundreds of billions of dollars, many, many times what it’s going to cost” by preventing influxes of drugs and criminals.

Earlier on Tuesday, Trump had touted via Twitter a report from the Center for Immigration Studies that claimed his proposed wall could pay for itself over a decade by curbing crime and immigration.

The Southern Poverty Law Center classifies the Center for Immigration Studies as a hate group.

During his visit to California, Trump spoke out against Gov. Jerry Brown (D) and the state’s “sanctuary” laws that offer some protection to undocumented immigrants.

The Trump administration recently sued California over three “sanctuary” laws that the administration argues prevent immigration officers from effectively enforcing federal immigration laws.