Balkan countries have agreed to conclude a free trade agreement by the end of the year, but the breakaway region of Trans-Dniester in Moldova remains a worry for its neighbours and the European Union.
The BBC's Helen Fawkes has witnessed the EU's efforts to help secure the border around Moldova, a former Soviet republic.
Ukraine is keen to prevent smuggling from Trans-Dniester
A team of officials is hard at work in Ukraine on a windswept and freezing frontier which is just a few minutes walk from Trans-Dniester.
Many in the West see this separatist state on Moldovan territory as a black hole.
So when Romania joins the EU next year, the new border will move east to Moldova - and that could spell trouble.
More than 100 officials have been deployed to the Ukrainian and Moldovan sides of the border.
"We hope to prevent human trafficking; we hope to stop the smuggling of goods and for sure we try to increase the efficiency of the border crossings, to bring them up to a European standard," says Kurt Schwendemann, who normally works as a German border guard.
The project became fully operational in February. Since then, Ukraine has introduced a new stricter customs regime for the breakaway region.
Cargo leaving Trans-Dniester now needs a customs stamp from Moldova.
Largely Russian and Ukrainian-speaking
Declared independence in 1990
Not recognised internationally
Separatist capital is Tiraspol
Population under a million
1,400 Russian troops established in Trans-Dniester
This has made it much more difficult to export goods and has caused long queues at the border.
People from Trans-Dniester have held angry protests.
Authorities in the breakaway region say they have lost millions of dollars and are on the verge of an economic crisis.
Russia is not happy, claiming that the action amounts to a blockade.
But Ukraine has the backing of the EU.
The rebel republic, which is not recognised internationally, has a reputation for being a haven for organised crime.
"The Trans-Dniester region is the centre of an international network of organised crime, first of all smuggling, illegal trafficking of human beings and it's a centre for illegal arms trafficking," says Oazu Nantoi, a political analyst from Moldova.
Cargoes from Trans-Dniester are under EU scrutiny
The dynamics in this strategically important region have changed since Ukraine and Moldova both elected pro-Western governments last year.
Trans-Dniester is a mainly Russian-speaking area.
It broke away from the Soviet Republic of Moldova just before the end of the USSR.
But the region has managed to hang onto its self-proclaimed independence thanks to a sizeable Russian military presence.
The EU project, costing 8m euros (£5.5m; $9.7m), was set up after the presidents of Moldova and Ukraine asked Brussels for help to deal with Trans-Dniester.
"There's lots of uncertainty for our European partners because the current situation is very problematic and directly affects the security of all the countries in Europe and the international community," says the Moldovan Foreign Minister, Andrei Stratan.
"For example in Trans-Dniester there are factories manufacturing weapons and also one of the Russian army's largest ammunition dumps is located there, so it's very alarming," he says.
A Ukrainian border guard helicopter flies over the disputed area - and from the air the scale of the operation seems daunting.
The Trans-Dniester border stretches for almost 500 kilometres (310 miles), much of it farm land.
The real difficulty is that many sections are not marked, it is just somewhere in a field.
So it is hard to tell where one country ends and the separatist state starts.
The project has been fully operational since last month and is already having an impact, according to the EU.
"The illegal activity and the reaction of criminals are very visible. When we are at the border, they avoid and they step back, not brave enough to cross the border," says General Ferenc Banfi, the head of the EU mission.
"There is a clear indication that the mission has respect in front of the criminals," he says.
This Border Assistance Mission only has limited powers; they are not able to carry out checks themselves.
But it does appear to be having an impact in putting pressure on the breakaway region, which will soon be on the EU's doorstep.