Croatia has joined the UK in blocking Serbia from opening Chapter 23 in its EU membership negotiations, despite agreeing a month earlier to end its veto.

Serbia opened its first two accession negotiation chapters on December 14, on financial control and on the normalisation of relations between Serbia and Kosovo, marking a significant milestone on the country's path to EU entry. But in April, Croatia refused to approve the opening of Chapter 23 covering the judiciary and fundamental rights at a regular meeting of the Committee on EU Enlargement of the Council of the EU (COELA) working group.

Croatia ended its veto at the end of May but it now appears to have taken the opportunity of the UK Brexit crisis to restate its opposition.

According to news reports, UK representatives at the Committee of Permanent Representatives in the European Union (COREPER) said they did not have a mandate to vote for opening the chapter. Decisions to open negotiation chapters have to be unanimous. Croatia then joined the UK in blocking the opening of the chapter.

Serbian President Tomislav Nikolic said that it is “impossible and unacceptable” that Croatia could stop Serbia from joining the EU, according to The Journal of Turkish Weekly. Nikolic also said “Whatever we do, Croatia always makes some moves to show that the time has come for it to affect the destiny of Serbia”.

Serbia desperately wanted to open the negotiations on Chapter 23 and Chapter 24 before the end of the Dutch presidency of the EU on July 1. But now Serbia’s hopes will be delayed to September.

Croatia has been trying to impose its own conditions on the negotiations:  full cooperation with the International Criminal Tribunal for the former Yugoslavia in The Hague, full compliance with all national and international obligations regarding the protection of minority rights, and avoidance of judicial conflicts in war crimes prosecution.

Belgrade’s hopes had recently been raised after Serbian PM Aleksandar Vucic and Croatian President Kolinda Grabar-Kitarovic signed a six-point declaration committed to resolve open issues and improve overall bilateral relations between the two countries. The document was inked on June 20 in the northern Serbian town of Subotica where Croatians represent a significant national minority.

But the fragility of these relations was shown on June 22 when the Serbian Ministry of Foreign Affairs announced that the government has recalled the head of Serbia’s permanent mission to the EU, Ambassador Dusko Lopandic, for not protesting enough about a private exhibition in the European Parliament about Croatian cardinal Alojzije Stepinac, known as a supporter of the Ustashe pro-Nazi regime.

The risk is that the negotiation setback will bring additional domestic resistance to the further EU integration of Serbia, which already has been on the rise as Russia ramps up its "soft influence" in the country and several pro-Russian and anti-EU political parties increase their support.

Vucic said on June 24 at a press conference called after Great Britain decided to leave the EU that Serbia will continue on its European path, that stability and prosperity and a better future for citizens remain the key objectives, and that the country will continue to nurture the best possible relations with Great Britain.

On June 29, Nikolic said in an interview with Radio Sputnik that even in the worst-case scenario of many EU countries exiting the bloc and Britain falling apart, Serbia would not give up on the idea of European integration.

Nikolic also said “It is imperative for Serbia to maintain friendly ties with all countries while, at the same, seeking EU membership. Our [accession] talks with the European Union are by no means at variance with our desire to maintain our friendship and economic partnership with Russia, China, Azerbaijan, Kazakhstan, Belarus and Cuba”. 

But Serbia’s close relations with Russia are worrying the EU. Michael Roth, German Minister of State for Europe, said last week that a country that wants to join the EU cannot have a neutral position, B92 reported. “Germany is also trying to have a solid relationship and cooperation with Russia and China. However, if you want to join the EU - that means that you need to declare yourselves in accordance with the foreign policy positions of the Union”, Roth said.

After the recent general elections Belgrade took some suspicious steps in the eyes of its Western allies. First, Aleksandar Vucic, the prime minister of Serbia's caretaker government who is also mandated to lead the new government, paid an unofficial visit to Moscow and held a meeting with Russian President Vladimir Putin. Then, he cancelled a planned visit to Brussels, as well as a planned visit to New York.

Some speculated that Vucic cancelled planned talks over rumoured support from the EU and the US for protesters who oppose the demolition of Belgrade’s Sarmala district to make way for the €3.2bn Belgrade Waterfront development. Others claim the move was made under pressure from Russia. More prosaically, Vucic, whose Serbian Progressive Party won the April 24 election, has not yet formed a new government, which is an additional reason for postponing talks.

Vucic has said hat he would travel to Brussels for meetings with top EU officials as soon as his new government has been formed, and that he had spoken with some of them over the weekend. "We agree on about 90% of things, but we do not share the same opinion about everything. This is the spirit of Europe, a European value, that we can share our positions," said Vucic.

Another problem for Serbia’s EU accession process is the unsolved conflict of Kosovo. Roth also said that "before Serbia's EU accession it is necessary to normalize relations between Serbia and Kosovo in the form of a legally binding agreement. All countries of the Western Balkans, Kosovo too, have a concrete accession perspective, but we do not want to import bilateral conflict into the EU", according to B92.