BRUSSELS (AP) — The leaders of Serbia and Kosovo met in Brussels on Thursday for another European Union-mediated attempt to resolve lingering issues between the two wartime rivaling states that have spiked tensions in the Balkans.

EU foreign policy chief Josep Borrell, speaking before the meeting between Serbian President Aleksandar Vucic and Kosovo Prime Minister Albin Kurti, said “recent tensions in the north of Kosovo have demonstrated yet again that it is time to move forward towards full normalization” of relations between the two states.

“I expect both leaders to be open and flexible to find common ground,” Borrell tweeted.

Kosovo is a former province of Serbia, which has refused to recognize the country’s 2008 declaration of independence. That came after a NATO-led intervention in 1999 stopped Belgrade’s bloody crackdown against majority Kosovo Albanians.

The European Union has overseen years of talks to normalize their ties, saying that’s one of the main preconditions for eventual membership in the 27-nation bloc.

Even before the latest round of talks started Thursday, Vucic expressed pessimism that the meeting would produce any major result.

“I am hoping for any solution, although I do not believe in it,” Vucic said on Instagram.

The latest tensions between Serbia and Kosovo soared late last month when Kurti’s government declared that Serbian identity documents and vehicle license plates would no longer be valid on Kosovo territory.

Minority Serbs, who live mostly in northern Kosovo, reacted with anger, putting up roadblocks, sounding air raid sirens and firing guns into the air and in the direction of Kosovo police officers. No one was injured.

Under apparent pressure from the West, Kurti postponed the implementation of the measure for a month, to Sept. 1.

Serbia and its allies Russia and China don’t recognize Kosovo’s independence, which is supported by the United States and most other Western states.

There are fears in the West that Russia could encourage Serbia into an armed intervention in northern Kosovo that would further destabilize the Balkans and shift at least some attention from its war in Ukraine.