Santo Domingo is seeking the immediate halt of construction works, saying 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.

Anxious families gathered at the border in Ouanaminthe, near the canal, where motorbikes milled nearby ready to give Haitians a ride from the border. A Haitian police officer said gates would open Thursday afternoon for people getting deported back to Haiti or families looking to leave.

The Dominican Republic has a strained relationship with its neighbor and has tightened border security, deporting tens of thousands 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, adding if the Haitian government could not control the construction, 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 threatened to shut the border last week, arguing construction works off the River Massacre violate a 1929 treaty.

"Unfortunately, they left us no alternative but to take drastic measures," Abinader said, adding the Dominican Republic is planning the construction of two dams that "without the treaty could significantly affect" Haiti.

The government said the border closure will include all land, sea and air routes, and that 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 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.