By Gabriel Partos
BBC South-East Europe analyst
Belgrade has come a long way since the Milosevic era
Five years after the fall of the authoritarian Yugoslav President, Slobodan Milosevic, Serbia and Montenegro has started negotiations with the European Union.
It is the first tentative step towards eventual EU membership.
Belgrade's immediate aim is to conclude a Stabilisation and Association Agreement (SAA) - part of the EU's long-term enlargement strategy towards the countries Brussels calls the "western Balkans".
But while the EU has now opened negotiations with one state, by the time the talks are concluded it may be having to deal with two or possibly three separate countries.
Among the former Yugoslav republics hoping to join the bloc Croatia is in the lead: last week it started full membership talks with the EU.
The former Yugoslav republic of Macedonia is next. It is awaiting formal candidate status from Brussels, which would then lead to its own accession talks.
Both Croatia and Macedonia concluded their SAAs in less than a year, though ratification took much longer.
In contrast, Albania - the next in the queue - has been holding talks for over two and a half years.
This is a big day for Serbia and Montenegro, whose citizens have waited for a long time
So how is Belgrade likely to fare?
There are three factors that could lead to delays in negotiating a deal.
The first is the requirement over full co-operation with the war crimes tribunal in The Hague. That is something Serbia and Montenegro shares with Croatia, as well as Bosnia-Hercegovina, which now remains the only western Balkan country still awaiting the start of its SAA talks with Brussels.
The EU's Enlargement Commissioner, Olli Rehn, made it clear in Belgrade on Monday that the EU would suspend the negotiations if it judged Belgrade's compliance over war crimes to be insufficient.
Compliance is generally taken to mean the apprehension and transfer of the remaining war crimes suspects who are believed to be hiding in Serbia - first and foremost, the Bosnian Serbs' wartime military commander, General Ratko Mladic.
In addition to that, Belgrade has two specific problems of its own.
First, the three-year trial period of the union of Serbia and Montenegro runs out in February. Montenegro's government has already signalled that it is intending to hold a referendum on independence soon after that.
The UN tribunal wants Mladic arrested by mid-December
Although the EU would prefer the two republics to stay together, it has been pragmatic enough to launch a twin-track approach which has involved separate negotiations with Belgrade and Podgorica over the past year.
The separate talks - within a single SAA framework - could then be transformed into two separate agreements, if Montenegrins were to vote for independence.
However, Mr Rehn has explained that he would have to seek a new mandate from the EU if the one SAA were to be replaced by two, and as he put it, that would mean "wasting valuable months".
Those "valuable months" could increase considerably - particularly for Podgorica - if the EU decided that Montenegro's vote for independence did not meet its own requirements. Such requirements could include a qualified majority - in other words, a pro-independence vote well in excess of a simple majority.
Even if possible problems over Montenegro's independence do not cause lengthy delays in Serbia's SAA talks, Belgrade is likely to encounter difficulties over the future of Kosovo[Kosova].
Talks on Kosovo's status are expected to be launched in the next few weeks, and some of the Western powers would like to have an outline agreement in place within 12 months.
If Belgrade obstructs negotiations on Kosovo[Kosova] or refuses to go along with a deal - perhaps because it signals a conditional, long-term independence for Kosovo - the SAA talks themselves could become stalled. That, in turn, would cause lengthy delays on the road to Europe.
The prospect of EU membership has already proved to be a powerful incentive for policy change in Serbia, Croatia, Macedonia and Bosnia. Whether it can contribute to resolving age-old disputes, such as the status of Kosovo[Kosova], may soon be put to the test.