European Union leaders sign historic association accords Friday with Ukraine, Georgia and Moldova as the three Soviet-era republics look to a future in Europe rather than with their old masters in Moscow.

The association accords, plus free trade deals, offer the three countries increased economic and political ties with the 28-nation bloc which could ultimately lead to EU membership.

For the EU, Friday's ceremonies mark the partial success at least of its Eastern Partnership policy, designed originally to also include Armenia, Azerbaijan and Belarus, but who all changed tack under Russian pressure and blandishments.

The policy was launched by Poland and Sweden in 2009, shortly after many of the former Communist states of central Europe joined the EU, so as also to offer their neighbours further to the east closer ties.

Inevitably, it has turned into a tug of war, with Russian President Vladimir Putin pulling out all the stops to prevent Ukraine, Georgia and Moldova from signing up, even at the cost of damaging sanctions.

The accords offer a cooperative framework covering a mixture of economic and political areas such as energy, visas and foreign policy and favour the independence of the judiciary and boosting civil society norms through the rule of law and eradicating corruption.

The linked trade deals aim at giving the three countries improved access to the EU's single market, the biggest in the world with some 500 million consumers.

- Economic gains, reform commitments -

An armed pro-Russian militant stands guard in the eastern Ukrainian city of Donetsk during talks of the Trilateral contact group on June 27, 2014 Alexander Khudoteply, AFP

For Ukraine, that could boost exports by one billion euros ($1.35 billion), helping its steel, textile and food product industries, and decreasing its reliance on the Russian market, an EU study showed.

Ukraine's struggling economy as a whole could grow by an additional one percentage point, a major boon for a government seeking to put its chaotic finances on an even keel, the study said.

For the EU, the rewards will be more long-term and depend on how successful the accords are.

The EU will have to make a sustained effort to help these countries make the painful but necessary reforms, especially in energy, so that they are less vulnerable to Russian pressure, said Judy Dempsey of the Carnegie Europe think-tank.

In return for EU help and largesse, the three have to take on a tough agenda of reform, potentially requiring change which will have profound political and social repercussions.

In the run-up to Friday's signature, EU ties with Russia have plumbed new lows, driven especially by events in Ukraine, a strategically placed country of 45 million of people.

Pro-Russian president Viktor Yanukovych ditched the association accord at the last moment in November under intense Russian pressure only to be ousted by pro-EU protests in February.

The new government in Kiev then took up the accord, which will be signed by President Petro Poroshenko, as Putin annexed the Crimea and threatened military intervention in the east of the country if ethnic Russians were at risk.

Ukrainian President Poroshenko (front), EU Commission President Jose Manuel Barosso (back), EU Council President Herman Van Rompuy and Georgia's Prime Minister Irakli Garibashvili at the EU summit on June 27, 2014 in Brussels Olivier Hoslet, POOL/AFP

Fighting between government and pro-Russian rebels since then has cost more than 400 lives.

If Moscow seems resigned to 'losing' the three countries, it has warned that it will take measures to limit the damage to its own economic interests, singling out a possible influx of now cheaper EU-made goods via Ukraine.

The EU, in an effort to calm some of these concerns, has agreed to hold political level talks early next month in a trilateral format including Ukraine and Russia to discuss the accord's possible implications for its economy.

Brussels argues that the association accords will benefit Russia because they will boost its neighbours' economies, drawing in more of its exports.

But at the same time, once signed, the accords mean the three countries cannot join Putin's vaunted Eurasian Customs Union, designed to bring back together the former Soviet Union states.

"The two are incompatible," one EU official said.