The failure to sign the EU-Ukraine Association Agreement will not only bury the Eastern Partnership initiative, but also lead to other negative consequences, according to European experts who specialize in the Eastern Partnership countries, who were polled by Interfax-Ukraine.

In particular, Tom Casier, a Senior Lecturer in International Relations at Brussels School of International Studies/University of Kent (Britain), proposed several scenarios for the development of the situation.

"In case of non-signing, the Vilnius summit, instead of becoming the celebratory highlight of almost half a decade of Eastern Partnership, will into its funeral. The Association Agreement with Ukraine would be a major success, but it may also be the only significant one for some time to come. Armenia has withdrawn from the Eastern Partnership and doubts increasingly surround Georgia. Political instability has even made Moldova's position in the Eastern Partnership more uncertain. Without Ukraine it becomes very hard to see any future for the Eastern Partnership at all," he said.

Casier said he was confident that for the EU "it would be a failure of its regional foreign policy altogether and a blow to the international role it sees for itself."

"With its relative absence and hesitation in Northern Africa after the Arab Spring, this is hardly something the EU can afford. Failure to tie Ukraine closer to the EU would prompt Brussels to fundamentally rethink its approach to its neighbors," he said.

The European expert said that another possible scenario would be the postponement of the signing of the agreement until a later date.

"Ukraine may be asked to fulfill further conditions and the date of signing may be delayed to a future date," Casier said.

However, in his opinion, this scenario is rather unlikely.

"More than ever the EU feels it should not lose momentum, in particular, in the context of increased Russian pressure. Brussels would also be more than happy to slap itself on the back for finally associating Ukraine," he said.

As another scenario he named a "partial agreement" when "certain parts of the agreement could enter into force at a later date, made dependent on further compliance or linking ratification to certain conditions."

"With the Association Agreement initialed already a long time ago, this would be a messy and legally complicated outcome, politically unwelcome for both parties," Casier said.

An expert at the European Policy Center, Amanda Paul, also believes that if the Association Agreement is not signed, for the EU "it will represent a failure of the Eastern Partnership, a failure to meet its goals of security, stability and prosperity in its neighborhood."

"The EU will lose credibility, failing to be able to deal with its own neighborhood. And let's not forget it will also come as a big blow for little Moldova (and Georgia), which needs a strong Ukraine engaged with the EU, in order to progress itself. Without Ukraine it will be much harder for Moldova to withstand pressure from Moscow," she said.

Speaking about the possible consequences for Ukraine of the non-signing of the agreement, she said that for Ukraine it would probably result in a serious internal conflict.

"The opposition would likely urge citizens into the streets to protest against the government and demand early elections due to its failure. So there would be political turmoil and instability in the country. This would further batter Ukraine's economy. Ukraine needs association with the EU to hold it together, to unite the country, a project crucial for the cohesion of Ukrainian society," Paul said.

However, in her opinion, that would be welcome news for Russia.

"But while Russia will try to capitalize gains it will not be easy – Ukraine is not Belarus and therefore Russia will probably fail to gobble up and swallow Kyiv, as Ukraine will continue to resist joining the Customs Union or taking steps to be economically or politically closer to Russia," she said.

Director of the Brussels Office of the German Hanns Seidel Foundation (Hanns Seidel Stiftung) Christian Forstner also shared the view that if the agreement is not signed, the policy of the EU's Eastern Partnership initiative "will suffer a defeat."

"It's unambiguous, because it's a major point of this direction of foreign policy between the EU and Ukraine. The EU will have to admit that the Eastern Partnership has to be reconsidered," he said.

Forstner also did not rule out a cooling of relations between Kyiv and Brussels.

"The relations will not be frozen, but there will be a cooling. It's impossible to put at risk the relationship with the whole country because of one person [former Ukrainian Prime Minister Yulia Tymoshenko]," the expert said.

He also expressed regret that the rapprochement of Kyiv and Brussels was seen negatively by Moscow.

"Unfortunately, we see a confrontation between the EU and Russia. Moscow thinks that Ukraine's rapprochement with the EU contradicts good relations, regarding this agreement as 'either with us or against us.' The EU has a completely opposite view," he said, while describing the situation.

Managing Director at the European Center for a Modern Ukraine Ina Kirsch also believes that not signing the agreement "would mean the end of the Eastern Partnership and giving up on the joint ambition of a new dimension to the process of European integration on both sides."

"If the European Union fails to integrate Ukraine, it will have no positive example of a successful neighborhood and foreign policy in general," she said.

"Not signing the agreement would mean for the European Union that is has not succeeded in its objective to be a home for all European countries. It will not be able to further develop the one big market for its products. In the long run it will mean that a new economic, political and human barrier will be constructed between the Union and the neighboring countries in the East. In the medium and long term this can develop into a threat for peace and stability at its borders, and not only the eastern ones," the European expert said.

Speaking about the consequences of these developments for EU-Ukraine relations, Kirsch said that this would lead to the fact that the "great objective of political association and economic integration will come to a sudden stop" and that "new and other forms of cooperation must be found to maintain good neighborly relations."

"Not signing the agreement would mean Ukraine giving up on its long ambition to become an equal partner of the European Union's member states, including its western neighbors. It would also mean giving in to Russian pressure: with some short term economic advantages but also keeping itself excluded from the advantages of integrating its economy with the European Union. Most of all it would mean refraining from a continuing modernization of its political and economic structures," Kirsch said.

Speaking about the Russian vision of this scenario, she suggested that not signing the agreement would mean "for Russia the feeling of a short-term victory over the European Union."

"For the long term it would, however, mean missing a chance of developing – on the basis of Ukraine's experience and possibilities – a common area of free trade and economic development from 'Lisbon to Vladivostok,'" she added.

Kirsch believes that the failure to sign the agreement for Ukraine would lead to negative consequences.

"The political elite, responsible for driving Ukraine into the European direction, would lose political influence immediately and the personal interests of parts of the business elite would take control over the country, governed by personal interests, not taking into account the interests of the country and its population," the European expert said.