Trump cites national emergency in new border wall plea

US President Donald Trump has reiterated the need for a stretch of about more than 800 km of border wall with Mexico to tackle what he said was a serious national emergency.

During a visit to a stretch of the border fence erected in Otay Mesa, southern California, Trump on Wednesday said the "tremendous national emergency" involving drugs and human trafficking could only be contained with the construction of the wall and "when human traffickers can't come through", reports Efe news.

This was Trump's second visit to the site, having previously gone in 2018 to observe the eight prototypes of the new wall he promised to build across the more than 3,200 km of the border with Mexico.

The prototype project cost exceeded $3 million and was finally demolished in February without any being selected.

However, the San Diego fence began to be replaced in June 2018 by a new metal wall between 18-30 feet high, almost twice as high as the previous stretch, at a cost of $147 million.

Trump was accompanied on Wednesday by the Acting Secretary of Homeland Security, Kevin McAleenan, who told journalists that the area where the prototypes were erected now has about 24 miles of primary or secondary wall.

Trump said the characteristics of the new wall in this area would make it harder for people to enter because it's not easy to climb or cut.

The President signed one of the columns of the wall during his tour before tweeting an image showing the concrete behind him.

He said that once the new barrier is erected, military contingents deployed at the border will be removed and only Customs and Border Protection officers will be kept.

Regarding Mexico's cooperation in addressing the immigration crisis, Trump stressed that they were "paying for 27,000 soldiers", thwarting illegal border crossings.

He also said raising tariffs on Mexico by 5 per cent for six months would cover the total cost of the wall, but ruled out taking measures in this regard.

Fewer than 15 people - among them supporters and workers at Otay Mesa, a shopping area south of the city of San Diego - waited on the streets for the arrival of the convoy that transported the president and federal officials, some of them from the Border Patrol.

This week, The Washington Post released a National Park Service report that warned that the plan to build a steel structure on the southern border could damage up to 22 archaeological sites.