Bulgaria and Romania today received confirmation they could join the European Union in January.
But the European Commission recommended a series of listed reforms the Balkan duo must complete to avoid being deprived of full membership benefits initially, including a large amount of EU aid.
"Accession of Bulgaria and Romania will mark a historic achievement, the completion of the fifth enlargement of the EU, which further pursues the reunification of our European family," European Commission President Jose Manuel Barroso told the European Parliament.
EU leaders are to approve the recommendation in October. France, Germany, Denmark and Belgium are yet to ratify the accession treaty, but this is unlikely to be a hurdle.
It will be the EU's second wave of enlargement into ex-communist eastern Europe, locking the Black Sea neighbours into the zone of stability and prosperity and promising a boost to their fast-growing economies.
"This is the genuine and final fall of the Berlin Wall for Bulgaria," Bulgarian Prime Minister Sergei Stanishev told reporters in Sofia.
The eastern European states could have been told to wait until 2008 before joining, but the commission today invited the countries to join in just three months.
However, full benefits may not be conferred because the countries suffer from rampant corruption and organised crime -
which adds to concern that billions of euros in EU aid may not be properly administered.
Both states may also face curbs on migration, largely because their economic output per capita is around one-third of the EU average.
Ireland, Britain and Sweden have indicated they will likely apply work restrictions on emigrants from both countries, despite opening their job markets for workers from the 10 countries that entered the EU in 2004.
The decision could be the last expansion for some time - which may prove a disappointment for Croatia. Turkey has also been in talks about EU membership but needs to accept the need for massive reforms, which are being met with considerable domestic dissent.
Current treaty provisions only allow for a maximum of 27 members before institutional changes are needed.
Commission chief Jose Manuel Barroso acknowledged yesterday that further enlargement may be held up by what is known as "enlargement fatigue", which was blamed for the rejection of the EU constitution in French and Dutch referendums last year.