Improved relations between the two countries are required for their EU ascension but it’s ‘a long road full of thorns’.

Kosovo’s leader urged calm as the Serbian president spoke to thousands of people in a majority-Serb area in Kosovo’s north.

Serbian President Aleksandar Vucic received a warm welcome from ethnic Serbs at a rally in Mitrovica on Sunday, a day after he arrived in Kosovo.

Kosovo President Hashim Thaci called for calm as roadblocks and burning tyres stopped Vucic from travelling to other majority-Serb areas.

The rally comes after Vucic abruptly cancelled a meeting with Thaci on Friday in Brussels.

It was assumed they would discuss a proposed land swap that would improve relations between the two countries and pave the way for their membership in the European Union.

The population of north Mitrovica, where Vucic held his rally, would likely be ceded to Serbia in a land swap.

Ethnic lines

Reporting from Mitrovica, Al Jazeera’s Sonia Gallego said while a land swap could help improve relations between Serbia and Kosovo, analysts and officials have warned further ethnic division could spell unrest for the Balkans.

“The issue, of course, being that if these territories here, these countries … were to be divided across ethnic lines then it would really stoke up further tensions within the region,” Gallego said.

The dispute between Serbia and Kosovo dates back to 1998-99 when Slobodan Milosevic, a former Serbian president, ordered a crackdown on Kosovo Albanian separatists.

More than 10,000 people died in the conflict before NATO bombing forced Serbia to pull out of the territory.

Kosovo declared independence from Serbia in 2008 and its sovereignty is recognised by 117 other nations. Serbia has never recognised its independence, however.

EU pressure

The EU has been pressuring the two leaders to resolve their dispute. Thaci and Vucic spoke with EU officials in Brussels last week, during which the possible land exchange was discussed.

It’s not known what caused Vucic to cancel the meeting on Friday.

Speaking at the Gazivoda Lake Dam near Mitrovica, Vucic told reporters: “I will do my best … but it is a long road full of thorns and problems ahead.”

Thaci said while deepening differences complicate negotiations, the two leaders made an agreement “to overcome these differences in the days and weeks to come with the understanding of the delegations and with the facilitation of the [EU]”, news site Balkan Insight quoted him as saying.

Further high-level talks between Serbia and Kosovo are scheduled in Brussels later this month.