After emergency discussions between Kosovo and Serbia failed to address their long-running disagreement over the car license plates used by the ethnic Serb minority in Kosovo, the European Union issued a warning of “escalation and violence” on Monday.

According to a statement to the media from Josep Borrell, the head of EU foreign policy, “the two parties did not agree to a solution today after several hours of debate.”

“I believe that both leaders bear a significant amount of responsibility for the breakdown of today’s negotiations as well as for any escalation and violence that may take place on the ground in the coming days.”

Kosovo has attempted this year to require its Serb minority to change their old car plates that date before 1999 when Kosovo was still part of Serbia.

This move has been met with strong and sometimes violent resistance by Serbs living in the northern part of the country, but Kosovo has said it will start issuing fines from Tuesday.

Borrell said an EU proposal could have avoided increased tensions, but the proposal, which was accepted by Serbian President Aleksandar Vucic, was not accepted by Kosovo Prime Minister Albin Kurti.

Borrell said he would inform the EU member states of the two countries’ “lack of respect for their international legal obligations” and warned that, given their commitment to joining the bloc, they should act accordingly.

Kurti said he was ready to hold further meetings to normalise relations between Belgrade and Pristina, not just to deal with one issue.

“We cannot be irresponsible and not treat the actual issues … We cannot turn ourselves into state leaders that are dealing only with car plates and are not talking how to normalize their relations,” he told reporters in Brussels.

Speaking in Belgrade after the meeting in Brussels, Vucic said he would meet Kosovo Serbs late on Monday to ask them to remain calm.

“We received the latest intelligence a little while ago, the situation is very difficult and it is on the verge of conflict,” Vucic told reporters. “We will do everything to preserve peace.”

He also said Serbia would stop issuing and renewing its own car number plates for Northern Kosovo.

The dispute over licence plates has stoked tensions for almost two years between Serbia and its former breakaway province, which declared independence in 2008 and is home to a Serb minority in the north backed by Belgrade.

There are about 50,000 ethnic Serbs who still consider themselves to be a part of Serbia and refuse to submit to Pristina’s rule.

Following a ruling by the Pristina government mandating that local Serbs finally exchange car license plates issued by Northern Kosovo Serb municipal authorities loyal to Belgrade with Kosovo state ones, hundreds of police officers, judges, prosecutors, and other state employees from the Serb minority resigned from their positions this month.

Borrell urged Serbia to stop providing new license plates and Kosovo to immediately halt the re-registration of automobiles in north Kosovo in order to give both parties “space and time” to come to an agreement.