Eurocrats are poised to agree a 2025 deadline for starting the process that will see Serbia, Montenegro, Macedonia, Albania, Bosnia and Herzegovina and Kosovo join the bloc.
It has launched a diplomatic effort to speed up the process after years of delay.
European Commissioner Johannes Hahn said the move was sparked by the resurgence of Russia, the migration crisis, Turkey’s authoritarian regime and the wish to bolster European integration after the UK vote for Brexit.
He added: “Either we export stability to the region or we import instability.”
Mr Hahn argued the EU’s enlargement process was the best way to fight corruption, organised crime and the threat of authoritarianism in the region.
A special Balkan summit is being held in Bulgarian capital Sofia in May.
Another meeting will be held in the UK in July.
However, the six countries still have to meet EU membership criteria.
Their banking and legal systems are weak and incomes lag behind those of the eurozone.
Deep divisions also persist in the wake of the ethnic conflicts which led to the break-up of Yugoslavia in the 1990s.