(CNN) -- Opposition lawmakers set off tear gas canisters in Kosovo's Parliament chamber on Wednesday in an attempt to prevent the ratification of a border agreement with neighboring Montenegro.
Video posted to social media showed lawmakers wiping their eyes and noses as they left the chamber in Kosovo's capital, Pristina.
The tear gas was released by opposition party Levizja Vetvendosje, according to Avni Bytyçi, deputy chief of staff to Speaker Kadri Veseli. It was a tactic the party had used previously to prevent voting, Bytyçi said.
"The Border Demarcation Agreement will be approved by the parliament today, in spite of the attempts of a small opposition party to prevent the vote with violent means," Veseli told CNN.
"We will not give up to violence and populism. This approval will serve to reinforce the sovereignty of our country and will unblock our path towards European Integration."
Ratification of the border deal is a key condition for Kosovo citizens to gain visa-free travel to the European Union, Bytyçi said.
Levizja Vetevendosje, or Movement for Self-Determination, posted a clip of the tear gas being let off in the chamber on its official Facebook page.
The party opposes the border deal, signed with Montenegro in 2015, because it claims it will wrongly hand over some 30 square miles of Kosovo's territory, Reuters news agency said.
US Ambassador to Kosovo Greg Delawie condemned the use of tear gas and called on lawmakers to return to the chamber and ratify the agreement.
"People with bankrupt ideas resort to political violence to try to achieve their goals," he said in a statement. "This should not be happening in Kosovo. Kosovo is better than this. This should not be happening in a European country. Teargas is not a European thing."
Kosovo, which declared independence in 2008, is one of six Western Balkans nations working toward eventual EU membership.