By Matthew Rusling

WASHINGTON, March 13 (Xinhua) -- U.S. President Donald Trump is continuing his plan to build a wall along the border with Mexico, despite a sea of controversy surrounding the issue.

Trump on Tuesday inspected eight prototypes in San Diego, a border city in the U.S. state of California, for the "big beautiful border wall" he wants to build to separate the United States from Mexico.

The move underscores that Trump is serious about building the wall, despite doubts among some observers and analysts, many of whom believed the plan was too radical, and simply an empty campaign promise.

"Building a wall along the Mexican border was one of Trump's primary campaign promises, so he is devoting a lot of time pushing this initiative as a way to demonstrate he is doing what he said he would do," Brookings Institution Senior Fellow Darrell West told Xinhua.

Construction began in September on the eight large prototypes, with each 18 to 30 feet tall, at a cost of between 2 million and 4 million U.S. dollars each.

Trump in January 2017 signed an executive order for the immediate construction of the border wall, as the U.S.-Mexico border is roughly 2,000 miles long, with only around a third of equipped with fencing to prevent the entrance of people and vehicles.

The wall construction comes at a time when the United States is home to millions of illegal immigrants, many of whom are from Latin America and enter the country via Mexico.

Trump has repeatedly said he would get Mexico to pay for the wall, upsetting one of the nation's biggest trading partners.

But the White House and Trump supporters maintain that these steps are simply practical, and that every sovereign nation reserves the right to protect its own borders. Trump has also said the wall is needed to keep out drug dealers, at a time when Mexico has been plagued by drug cartels.

"Trump understands pushing the wall is vital to his base and (a policy) they wholeheartedly endorse. Many of the people who supported him want a tougher immigration policy and having a wall is consistent with that sentiment," West said.

The major obstacle is that the wall is very expensive and few believe it will stem the tide of illegal immigrants.

Besides the cost of the structure, the logistical and geographical challenges of building the structure on the southern border is another obstacle, analysts note.

People think many other ideas such as increasing the number of border guards and deploying electronic cameras and sensors will be more effective. Even Republican legislators are not entirely convinced the wall is vital for border security, West said.

But some support the wall, arguing that it's high time the United States protects its own borders.

"Updating the U.S. border security infrastructure is long overdue and President Trump has promised to change that," Ana Quintana, Heritage Foundation's Latin America policy analyst, told Xinhua.

"There is a direct body count associated with threats facing the U.S. homeland from transnational criminal organizations and illicit narcotics traffickers. President Trump is simply fulfilling his obligations by responding to these threats," Quintana said.

Mexico is also protecting its own southern border with its neighbor Guatemala, she added.

"Mexico's own security dilemmas internally and on their southern border with Guatemala highlight the shared premium both the U.S. and Mexico place on border security," Quintana said.

"It reflects a policy that is hard on all forms of immigration, with a particular attention on illegal immigration -- which is a major concern about the Trump political base," Dan Mahaffee, senior vice president and director of policy at the Center for the Study of Congress and the Presidency, told Xinhua.

Indeed, experts note that for the White House, enforcing the president's policies on immigration is far more important that continued good relations with Mexico.

"For the President, these policies are more important than ensuring the continued cooperation with Mexico in a wide range of political, economic, and security interests," Mahaffee said.