The trip Tuesday, which has brought him the Otay Mesa area of San Diego, includes a tour of the eight options that his administration has selected for testing - and that might serve as his long-promised wall along the border of the USA and Mexico, if Congress decides to allot the funds to do so. "And by the way, the state of California is begging us to build walls in certain areas, they don't tell you that".
The border with Mexico stretches almost 3,200km and about one-third of it already has some type of barrier or wall. Such decision represented a victory for Trump, but it did not mean the construction would start immediately, because Congress still has to authorize or allocate funds to begin the project. He described the existing wall as "lousy" but noted it stopped as much as 95 percent of attempted illegal entry. "You could be two feet away from a criminal cartel and you don't even know they're there", said Trump.
Trump appeared engaged as he was briefed on eight towering prototypes, including one with blue steel on top.
- If we don't have a wall system, we're not going to have a country.More news: Former South African President Innocent until Proven Guilty, ANC Says
In the letter, Brown encourages Trump to visit the state's Central Valley, where preparations are underway for a bullet train from San Francisco to Los Angeles - including the construction of bridges to accommodate the high-speed line - and touts the diversity of a state that on its own is the sixth largest economy in the world.
The president criticized California's governor Jerry Brown during his first visit to the state since being elected, saying Brown is doing "a very poor job running" California. It is past the time when a pushback against sanctuary cities and a declared sanctuary state is more than a nudge.
US President Donald Trump tweeted "Marine Core" instead of "Marine Corps".
"But he believes that whatever wall they choose needs to be see-through, he says".More news: Russia Expels 23 British Diplomats, Escalating Row Over Ex-Spy's Poisoning
Mr Trump flew to San Diego to view several prototypes measuring 30ft-tall (9m), and asked which of them would be hardest to climb.
The president's arrival was awaited in the area by a cluster of police, chanting protesters and supporters clad in campaign gear, waving American flags. "Now they fixed the holes, but it doesn't look very good".
"I've been praying for federal agents to arrest Oakland Mayor Libby Schaaf - for aiding and abetting criminal aliens in our country", Donnelly said.
During his visit, Mr Trump took aim at so-called "sanctuary cities" in California, where local governments refuse to cooperate with federal immigration officials seeking to deport illegal immigrants.
Trump later said sanctuary cities protected a "horrible group of people".More news: Russian Federation expels 23 British diplomats as nerve agent fallout continues