Brussels – The European Union‘s foreign policy chief expressed hope Tuesday for a “rapid progress” in EU-brokered negotiations aimed at resolving a long-lasting dispute between Serbia and Kosovo that remains a source of tensions in the volatile Balkans.

European Commission Vice-President Josep Borrell urged leaders of the rival Balkan nations ahead of a meeting in Brussels to “seize the opportunity” of a “new momentum” and move forward in the negotiations that have been stalled since last year.

“The European Union and I, personally, we are invested to see rapid progress to finally leave the past behind,” said Borrell.

The meeting Tuesday with Serbia’s President Aleksandar Vucic and Kosovo’s new Prime Minister Albin Kurti marks the revival of the process that started in March 2011 but has faltered several times in the meantime. More meetings between Serbia and Kosovo delegations are expected during the summer.

“There is a new momentum and we have to use it,” Borrell said.

Both Serbia and Kosovo have been told that they cannot hope to move forward in their efforts to join the EU before resolving the decades-old rift that exploded in a conflict in 1998-99, leaving more than 10,000 people dead and triggering a NATO intervention.

Kosovo, formerly a province in Serbia, declared independence in 2008 but Belgrade has refused to accept that. While Kosovo has been recognized by the United States and most EU nations, Belgrade has relied on support from Russia and China in its bid to retain claim on the territory.

Since the start of the EU-brokered negotiations, Belgrade and Pristina delegations have agreed on a number of issues, tackling everyday problems such as free travel or trade. But they remained far apart on Kosovo’s independence.

Borrell said relations between Serbia and Kosovo are important for the stability of the entire Western Balkan region, where Moscow and Beijing also have sought to increase their political and economic influence, alarming the West.

Without an agreement between Serbia and Kosovo, Western Balkan stability and economic progress will be jeopardized, warned Borrell.

EU special envoy for the dialogue, Miroslav Lajcak is set to attend.