BELGRADE (Reuters) - Serbia will have to reach and implement a legally binding agreement on relations with its former province of Kosovo and undergo a string of reforms if it aims to join the EU by 2025, EU enlargement commissioner Johannes Hahn said on Wednesday.

FILE PHOTO - European Neighbourhood Policy and Enlargement Negotiations Commissioner Johannes Hahn speaks during an interview with Reuters at the EU Commission headquarters in Brussels, Belgium January 18, 2018. REUTERS/Francois Lenoir

A day earlier, the European Commission, seeking to reinvigorate the EU with Britain set to leave, presented a strategy to bring Western Balkan nations into the fold if they achieve required reforms by 2025.

But Hahn said the bloc will not import unresolved disputes.

“The EU cannot and will not import bilateral problems ... Serbia must conclude and irreversibly implement a legally binding agreement with Kosovo,” Hahn told a news conference in Belgrade.

He stopped short of saying whether Serbia must fully recognize Kosovo, which declared independence in 2008 almost a decade after a NATO bombing campaign ended a crackdown by Serbia against independence-seeking ethic Albanians there.

Kosovo has been recognized by 115 countries, including 23 out of 28 EU members, but its UN membership is being blocked by Serbia’s allies Russia and China.

Serbian President Aleksandar Vucic, who met Hahn and appeared alongside him at the news conference, praised EU strategy as an opportunity for integration for Serbia, which is still reeling from isolation and devastating wars in 1990s.

Vucic, a former Serb nationalist who changed his views in the past decade to become a supporter of closer integration with Europe, described a deal with Kosovo as a “mountain of obstacles” which could be achieved only if “everybody loses something”. A plebiscite would be needed, he said.

“The people will have to decide, ... whether they see their future in Europe, for which we will have to pay a costly price, or we can go on like this, at Europe’s tail.”

On Wednesday, Aleksandar Vulin, the defense minister and Vucic’s top ally, said Belgrade and Pristina should partition Kosovo.

Before it joins the EU, Serbia will also have to solve open border issues with Croatia and Bosnia, its foes from the 1990s wars that followed the breakup of Yugoslavia.

Belgrade will also have to reform its slow and unwieldy judiciary, improve rule of law, tackle the freedoms of the media and safeguard minority rights.

“If we solve ... problems we will accelerate like a rocket,” Vucic said.