The Argentine town of Aguas Blancas, on the Bolivian border, has launched a tender to build a 200-meter fence to strengthen immigration controls. Bolivia warned that this “unilateral measure” could affect the “peaceful coexistence” between the two countries.

The tender was announced by Aguas Blancas Mayor Adrián Zigarán on Friday and published in the Salta Official Gazette on Monday. 

Aguas Blancas is a small town in northeastern Salta province, opposite the Bolivian town of Bermejo. The river Bermejo acts as a natural border between them. Thousands of people cross the border each day. It is a notoriously porous border point, with many people skipping the formal border controls by crossing the water a few hundred meters to the side of the border point.

The fence will go from the Aguas Blancas bus station to the immigration office. It will block passengers from accessing the river directly, instead forcing them to pass through the immigration checkpoint. 

The Bolivian Foreign Ministry released a statement on Monday to express “concern” over the decision. “Border issues should be addressed through the bilateral dialogue mechanisms established between the states to find coordinated solutions to common issues,” they said.

The statement added that the ministry will request information on the issue “to carry out the corresponding actions.”

In an interview published by local outlet Nuevo Diario de Salta on Friday, Zigarán said that many migrants who arrive at Aguas Blancas hop the flood barriers, skip the border point 200 meters away, and use small boats to cross into Bolivia.

“The idea is that people will now only go through the official border crossings, in line with migration controls,” Zigarán told local outlet El Tribuno in an article published on Monday.

In that same article, the National Security Ministry’s Border Vigilance and Control Director Virginia Cornejo said that the fence aims to “delineate the border and guarantee order in an area that had been abandoned” by authorities in the past.

“Bolivia enforced strict controls, but on the Argentine side there was no clear delimitation,” she added.

In December, Argentine Security Minister Patricia Bullrich and Salta Governor Gustavo Sáenz launched the “Güemes Plan” in Aguas Blancas and Orán cities. The first measure was to deploy the Argentine Navy Police to patrol the Bermejo river. During the announcement, Bullrich said the goal was to combat “drug traffic, hitmen and uncontrolled border crossings.” 

The Security Ministry did not respond to requests for comment.