Two months since Serbia and Kosovo agreed to normalise relations, implementation of the accord has barely started just days before European leaders are due to decide whether they merit closer EU ties.
According to the EU-brokered April 19 agreement, the first thaw in the diplomatic freeze between Belgrade and Pristina, they should by June 15 have completed talks on telecommunications and energy.
But both issues appear to have hit stumbling blocks, with each side blaming the other for the impasse.
Serbian trade minister Rasim Ljajic said an agreement on telecommunications had been "more-less agreed" with the EU but rejected by Pristina over the telephone dialling code for Kosovo.
Kosovo's negotiator Edita Tahiri blamed Serbia for "continuing to unilaterally interpret the accord" and "failing to show needed seriousness in negotiations".
With the negotiators unable to agree a solution, it will likely be up to Serbian Prime Minister Ivica Dacic and his Kosovo counterpart Hashim Thaci to hash out a deal in fresh talks in Brussels on Thursday.
Both sides are expected to speed up efforts to implement the accord to win the support of EU leaders at the summit on June 27 and 28.
That is when the 27-nation bloc is expected to decide whether Serbia and Kosovo have made enough progress in normalising ties.
If they think they have, Belgrade will be offered a date to start EU accession talks and Pristina a partnership accord.
Negotiators have been trying for weeks to resolve a dispute over Kosovo's telephone dialling code: it has been unable to get an international code as an independent country because of Serbia's opposition.
Kosovo declared independence in 2008, but when it comes to phone lines, it is still part of Serbia, which has refused to recognise the breakaway territory's sovereignty.
Anyone calling a fixed line in Kosovo has to dial via the Serbian country code (+381). For Serbians, making a call to Kosovo is still a national call.
Mobile phone operators who moved into Kosovo after Serb forces were driven out, issue Kosovo numbers with the national codes for Monaco (+377) or Slovenia (+386).
"This is unacceptable and has to be changed," said Zeqir Uka, a 50-year old businessman from Pristina.
"I have an impression that my business partners abroad do not consider me seriously when they realise we still do not have our own international country code."
But Serbs living in Kosovo insist on keeping Belgrade-based mobile providers and the Serbian country code to maintain links with the homeland and to avoid higher costs.
Talks on energy issues have also stalled.
Kosovo insists on becoming fully independent from Serbia in importing and exporting electricity.
All power currently goes through Belgrade in accordance with a scheme dating back to the former Yugoslavia.
Power cuts lasting for hours are still common in Kosovo, partly due to the outdated system, but also because of disputes over energy supplies.
Serbia wants its own electricity company to continue supplying Serb-dominated areas in Kosovo; Pristina insists on control over its entire territory.
Even points supposedly agreed in the April agreement have not yet been implemented.
Liaison officers from Belgrade and Pristina tasked with that job only took up their posts on Monday.
Serbian officials have begun closing their police stations in the north of Kosovo, but some 800 policemen are still employed by the Serbian interior ministry.
The two sides have still to agree how many of them will join Kosovo police forces (KPS).
Pristina said it only needed up to 150 Serb police officers. The Kosovo parliament was also late in adopting an amnesty law that would shelter Serbs from prosecution for crimes committed during the 1998-1999 war.
Sources in Kosovska Mitrovica, Serb-run courts in the northern Kosovo were ordered to stop taking new cases from mid-July. It is still not clear however how many of the 60 judges and several hundred employees in the judiciary will join the Pristina-administered courts.
Under the terms of the agreement, ethnic Serbs should be proportionally represented in the judiciary in areas where they live.