A planned visit by President Donald Trump to an Arizona town at the U.S.-Mexico border Tuesday is sending a strong signal he is not backing down from one of his central campaign promises.

Trump is scheduled to visit a Border Patrol station in Yuma – a city that sits in proximity to the California and Mexico borders and in an area that was once a hotbed of illegal immigration, but which administration officials say saw a steep drop-off after the expansion of border barriers roughly a decade ago.

The White House and the Department of Homeland Security have framed Trump's Tuesday visit as an attempt to highlight how walls and other infrastructure such as sensors and lighting can slow illegal immigration, and as an opportunity to tout the steep decline in illegal crossings since Trump took office.

Yuma previously had only about 5 miles of fencing, and it once saw as many as 800 people a day attempt to cross the border illegally, a senior DHS official said during a background call Tuesday. However, after President George W. Bush signed the Secure Fence Act in 2006 – leading to the construction of another 55 miles of barrier walls and barrier fences – the number of crossings dropped precipitously.

"In Yuma, it's a prime example of having that right mix of technology, agents, as well as the infrastructure," a DHS official said during the call. "Within a couple of years, the bottom fell out as it related to the number of arrests that were being made in that location."

The president is not scheduled to visit the wall, as had been initially reported. Instead, he is set to stop at a hangar where he will see agency equipment, including a Predator drone; meet with Border Patrol agents and U.S. Marines; and get a briefing from senior officials.

Immigration officials have recorded a sharp decline in apprehensions at the Southwest border this year, with Border Patrol apprehending 126,472 people who were attempting to illegally enter the U.S. between January and the end of July – a roughly 45 percent drop from the same seven-month period last year.

Of those who were apprehended, officials say the number of unaccompanied children and the number of people from countries other than Mexico also have seen major declines, falling 54 and 47 percent from last year, respectively.