The prospects of Greece abandoning the euro sent EU legal experts scrambling for the law books Thursday as it became clear that European Union rules provide for exit from the entire 27-nation bloc -- but not from the eurozone.
Analysts warned that a walkout by a country seen as Europe's ancient cradle of democracy would spell political disaster.
"On balance, I think Greece is likely to be outside the eurozone within 12 months but I don't believe it will be forced out of the EU. It would be playing with fire," Simon Tilford, chief economist at London's Centre for European Reform, told AFP.
Fears of the EU losing a member emerged as Brussels experts confirmed that the bloc's rule book, the Lisbon Treaty, omits to provide for a member of the 17-nation eurozone to opt out of the 12-year-old single currency.
"The treaty doesn't foresee an exit from the eurozone without exiting the EU," said European Commission spokeswoman Karolina Kottova.
A European Central Bank report, penned as economic strains grew in late 2009, concluded that "exit from European Monetary Union, without a parallel withdrawal from the EU, would be legally inconceivable."
Article 50 of the Treaty that came into force in December 2009 introduced an EU exit clause for the first time but it has never been used.
"Nobody can be forced; the other member states have to agree and both sides have to work out an agreement on the conditions of the exit," Janis Emmanouilidis of the European Policy Centre think-tank told AFP.
A Greek exit from the union, he added, "would be a catastrophe for the country and for the EU," while London-based Tilford said it would represent "a catastrophic failure for the EU."
Greece rushed to join the bloc in 1981 when still recovering from military dictatorship, despite opposition from the likes of France, who feared it was not ready.
Wealthier Austria, Finland and Sweden joined only 14 years later. Spain and Portugal waited a further five years.
"Though legally it cannot leave the eurozone, when it comes to hard politics, it is always possible to overcome the legal niceties," Tilford said.
"Some would like to see its ejection from the EU," he added, "to serve as a deterrent to other struggling members of the eurozone."
Talk of Greece leaving the eurozone heated up after Prime Minister George Papandreou threatened to call a referendum on the latest eurozone rescue package deemed vital for his country's survival.
Crumbling under the weight of its debt load and the pain of its austerity programmes, an exit from the EU could lead to Greece's collapse, causing further instability, leaving it prone to becoming ungovernable, analysts said.
"The EU is about more than a eurozone. It will be under intense external pressure, including from the US, to avoid Greece leaving," Tilford said.