The EU parliament's envoy for Ukraine on Thursday warned Kiev risked losing the chance of signing a key deal with the bloc indefinitely if it fails to ink the accord at a summit later this month.
The warning by Aleksander Kwasniewski, a former president of Poland, came after Ukraine's parliament on Wednesday failed to agree legislation that would have allowed former prime minister Yulia Tymoshenko to go free and remove a key obstacle to signing the Association Agreement.
The Association Agreement - which Ukraine wants to sign at a 28-29 summit in Vilnius -- would be a first step on the road to membership and mark a historic break by Ukraine with its former master Moscow.
"Failure to sign in Vilnius would mean the postponing of the Association (Agreement) for an indefinite number of years," Kwasniewski told Ukraine's UNIAN news agency in an interview posted on its website.
He said there was no chance of the issue being worked on in the next two years as 2014 would see EU parliament elections while presidential elections in Ukraine are due in early 2015.
"And after these two years we would return to a different situation. And one that is not necessarily better. And maybe worse than in 2013."
The mission of Kwasniewski and his fellow envoy on Ukraine, the former EU parliamentary speaker Pat Cox, has been extended right up to the summit in a last ditch bid to give Ukraine time to make progress on the Tymoshenko case.
Russia has expressed its irritation with the prospect of Ukraine aligning itself with the EU and warned of retaliatory measures if the Association Agreement is signed.
But Kwasniewski warned that Russia had been making a grave error by raising the spectre of trade retaliation.
"Not one people -- and Ukrainians are a proud people -- likes to be humiliated. So I think that Russia is making a mistake here."
But he acknowledged that the stakes are high for all sides.
"There is no doubt that we are talking about a geopolitical struggle.... So I am not surprised by many things that are happening. This is linked to the great importance of what awaits us in Vilnius."
The decisive moment may come next week when Ukraine's parliament meets on Tuesday in a final bid to agree a bill that would allow Tymoshenko to go abroad for treatment and remove the biggest barrier for the deal.
Signing the Association Agreement has been held up by the 2011 jailing of Tymoshenko for seven years on contested abuse-of-power charges she says were ordered as political revenge by President Viktor Yanukovych.