President Trump touted the effectiveness of newly-constructed barriers as he toured the U.S.-Mexico border near San Diego on Wednesday, insisting, “This wall can’t be climbed.”

“It’s a very powerful -- very powerful – wall,” the president, accompanied by border officials, said as he toured the Otay Mesa area.

Last month, the administration completed 14 miles of steel bollards up to 30 feet high. The $147 million project replaced a much shorter fence made of surplus airstrip landing mats from the Vietnam War.

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The president said it’s in one of the “most dangerous areas,” and they’ve built a “double wall” – one barrier was 18 feet, and the other was 30 feet. Before leaving, Trump used a marker to sign the wall.

President Trump touring a section of the southern border wall on Wednesday. (AP Photo/Evan Vucci)

He also talked up how the barrier was designed to retain heat as a deterrent. “You can fry an egg on that wall,” he said.

At the same site last year, Trump saw wall prototypes, which were destroyed to make way for 14 miles of steel bollards currently under construction.

The president and his administration have said they planned on building between 450 and 500 miles of fencing along the nearly 2,000-mile border by the end of 2020, an ambitious undertaking funded by billions of defense dollars that had been earmarked for things such as military base schools, target ranges and maintenance facilities.

Trump has been riding a string of wins on the wall and on immigration. Arrests on the Mexican border arrests plunged well beyond the usual summer dip in August.

Last week, the Supreme Court gave Trump a green light to deny asylum to anyone who passed through another country on the way to the U.S. border with Mexico without having sought protection in that third country.

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Meanwhile, the Defense Department has nixed three border barrier projects in Arizona over costs, according to a court document filed Monday.

The Pentagon on Aug. 26 authorized the Army Corps of Engineers (USACE) to undertake the additional projects to build fencing, infrastructure and lighting at the U.S.-Mexico border, the filing said.

Fox News' Melissa Leon and The Associated Press contributed to this report.