This June, Vučić called on ethnic Serbs living in Kosovo to participate in its national elections, following years of encouragement by Belgrade to boycott them. His efforts were rewarded when tens of thousands of Kosovar Serbs turned out at the polls.
Difficulties materialized however when the election results proved inconclusive, with the outgoing prime minister narrowly failing to secure enough seats to hold power.
This ignited a row between the ruling party and the opposition over who should form the next government. This has been taken to Kosovo's constitutional court, where the debate is seen dragging on for months.
During this time, Kosovo will remain without a formal government. This is a big blow to Vučić, because stability in the Balkans is viewed as crucial to securing Serbia's accession. Its bid is unlikely to progress while Kosovo on its doorstep remains so unstable.
'Worse than hell'
Crunch time for the prime minister and his Serbian Progressive Party could be autumn, when a raft of public sector cuts come into effect, aimed at decreasing the country's sky-high deficit prior to joining the EU. Strict cuts are planned to the number of government employees and to wages and pensions. New privatization, bankruptcy, labor and construction laws are also slated.
"That is all going to come in with a bang potentially cause a lot of social tension," William Bartlett, an academic specializing in south-east Europe at the London School of Economics told CNBC.
"It will be bad news for Serbia if it is going to run into economic and social problems in autumn, but has no good news to offer on accession."
Vučić also saw problems ahead. "It is not an easy situation—we have been delaying all reforms for decades."
"Whenever you try do any kind of reforms in the Balkans—it doesn't matter whether that is Croatia, Bosnia or Serbia—it is going to be worse than hell…But I am absolutely dedicated."