The president of the Dominican Republic on Sunday defended his decision to close air, sea and land traffic with neighboring Haiti in their dispute over construction of a canal targeting a river that runs through both countries.

President Luis Abinader said in a televised speech that the border closures begun Friday will remain in place until construction is halted on the canal, which seeks to use water from the Massacre River to alleviate a drought in Haiti’s Maribaroux plain.

Accusing Haiti of violating a 1929 treaty between both countries, he said that the Massacre River is a key resource for Dominican farmers and that construction could damage the environment, including a wetland.

President Abinader said the precedent of an irrigation project built unilaterally can lead to an escalation of constructions that would destroy the river.

The river is named after a bloody battle between French and Spanish colonizers, and it was the site of a mass killing of Haitians by the Dominican army in 1937.

The full border shutdowns came four days after President Abinader announced that his administration had stopped issuing visas to Haitians and had closed the border near the northern town of Dajabon.

He said it was important to raise awareness in the international community so it comes to Haiti’s aid.