The EU's high representative, Josep Borrell, held fruitless talks on Monday with Serbian President Aleksandar Vucic and Kosovo Prime Minister Albin Kurti in Brussels, in a bid to resolve a long-running row over vehicle license plates.

Borrell said that since August "the dispute over license plates has worsened."

"After many hours of discussion … the two parties did not agree to a solution," Borrell said.

The row centers on a decision made by the Kosovo government earlier this month to ban Serbian-issued license plates after an almost two-year-long dispute.

The move prompted 10 Serb lawmakers, 10 prosecutors and 576 police officers in Kosovo's northern Mitrovica region to resign on November 5.

Proposal rejected by Kosovo

The EU's top diplomat said that a proposal was put forward that could have avoided the current "risky situation" which President Vucic had accepted, but "unhappily, Prime Minister Kurti did not."

Borrell said Kosovo rejecting the proposal sent a "very negative political signal."

Before the talks, the EU said the meeting between the West Balkan leaders and Borrell would focus on "finding a way out of the current crisis and avoiding any further escalation and tensions on the ground, with an emphasis on license plates and the return of Kosovo Serbs to Kosovo institutions."

The dispute comes on the top of simmering tensions between Belgrade and Pristina, with the former refusing to recognize Kosovo's statehood after it broke away from Serbia in 2008.

That unilateral move came after a 1998-99 war in which about 13,000 people died amid a separatist rebellion by ethnic Albanians and a brutal Serbian crackdown. The war ended after NATO bombed Serbia.

What happens next?

On Monday, Borrell said that the row has caused a "dangerous security vacuum."

The plate ban means that some 6,300 ethnic Serbs could face fines if they retain number plates now deemed illegal and would be permitted to drive from April 21 only with temporary local plates.

Kosovo is home to a Serb minority in Mitrovica that is backed by Belgrade.

Local media outlet BalkanInsight has reported on arson attacks targeting Kosovo Serbs who had obeyed Kosovar officials and replaced their Serbian license plates.

Borrell's spokesman stressed the EU was not giving up the search for a solution, but added that "there cannot be any negotiations on normalization of relations with a threat of violence present."

kb,tj/dj,jcg (AP,AFP)