The Dominican Republic will shut its entire border with neighboring Haiti from 6 a.m. (1000 GMT) on Friday, President Luis Abinader told reporters, amid a conflict over the construction of a water channel from a shared river.

Santo Domingo said the closure would last “as long as necessary” with backing from the country’s military and police forces, though talks with the Haitian government would continue.

The Dominican Republic has a strained relationship with its neighbor and has tightened border security, deporting tens of thousands of Haitians fleeing worsening gang warfare in their country.

We have been prepared for weeks, not only for this situation but also for a possible peace force in Haiti,” Abinader said, saying that even if the Haitian government could not control the construction of the canal, Santo Domingo could.

Abinader is set to raise the issue at the United Nations on a visit to New York next week.

The Dominican Republic first threatened to shut the border last week, arguing that construction works off the River Massacre are a violation of the 1929 Treaty of Peace, Friendship and Arbitration.

“Unfortunately, they left us no alternative but to take drastic measures,” Abinader said in a press conference.

Abinader said the Dominican Republic is planning the construction of two dams that “without the treaty could significantly affect” Haiti.

The government said the border closure is set to include all land, sea and air routes, and said it deployed a further 20 armored vehicles to a military camp on the border.

Haitians were seen rushing to the border, and airline Sunrise Airways said it was adding a flight between both countries on Thursday afternoon ahead of the border closure.

The U.S. Embassy, which has called on its citizens to leave Haiti, said on its website that those planning to leave for the Dominican Republic would need to make other arrangements.