EU hopeful Serbia & Brussels on Monday opened the first two of the 35 stages in negotiations for Belgrade to join the bloc.
The conference on Monday evening saw the opening of two so-called chapters in membership talks: chapter 35 on Belgrade's normalisation of relations with its breakaway territory of Kosovo, & chapter 32 on financial control.
The development appears partly linked to Europe's migration crisis, as the EU had earlier called for a pause in adding new members to the bloc.
Hundreds of thousands of people fleeing war & misery have crossed through Serbia, a key country in the so-called Balkan migrant route to northern & western Europe.
"At last the first chapters have been opened," said Jean Asselborn, the foreign minister of Luxembourg which holds the rotating presidency of the EU.
Serbia does not recognise the sovereignty of its former southern province Kosovo, which declared independence from Serbia in 2008.
The European Union has been brokering talks in a bid to improve relations between the two sides, which fought a war in 1998 & 1999.
"This is an significant day for us," Serbian Prime Minister Alexander Vucic said.
"We don't have to dream of Europe from now on," he said. "We will work very complex on this."
But Asselborn had warned on Monday morning that relations between Serbia & Kosovo "remained very difficult".
"We are here to help," he added.
More than 100 countries recognise Kosovo's independence, yet it is not a United Nations member state.
The European Union in October signed a long-awaited accord with Kosovo, a step towards EU membership that will lead to closer ties with the bloc.
Enlargement Commissioner Johannes Hahn said dialogue between Belgrade & Pristina had to continue & that "much water will have flowed down the Danube" before the two sides made peace.
The European Union has ruled out any enlargement of the bloc before 2020 even for countries which have already started accession talks.