Ireland will make or break the European Union's enlargement when it votes in a referendum later this month, EU officials warned.
Despite EU approval for 10 new members to join the bloc in 2004, the plan could be scrapped indefinitely if Irish voters refuse to ratify the Treaty of Nice that governs enlargement.
Each EU member must ratify the treaty, named after the French resort town where it was signed, but Ireland is the only country that puts it to a referendum. Voters have already rejected it once, and a second "no" vote on Oct. 19 will kill it.
"If the Treaty of Nice is rejected in Ireland again, then I do not know how we can continue with enlargement. I do not even know whether we'll continue," said Guenther Verheugen, the EU's top enlargement commissioner. "This treaty is a precondition of enlargement."
Signed in 2000, the treaty sets up the reforms necessary for a larger EU to function.
Irish voters first rejected the treaty in June 2001, sending shock waves throughout Europe.
"If they say 'no', there's no reason to hide it, we'll be in a crisis," said Danish Prime Minister Anders Fogh Rasmussen, whose country holds the EU's rotating presidency through the end of the year. "There is no plan B."
Other EU officials have also stressed that the union lacks a backup plan to keep enlargement on track should Ireland reject Nice, and Brussels has appealed to the Irish to vote "yes."
"The wisdom of the Irish electorate will help it take into account the desire, the needs, the hopes of these nations in Europe that want to become part of our family," Verheugen said.
The lengthy treaty spells out a streamlined decision-making process to ensure that the EU is not paralyzed by the competing demands of its new, more complex membership.
It details the votes each country has at leaders' and ministerial meetings, its representation on the European Commission, the EU's executive arm and in the European Parliament.
"The Irish people must realize how important the stakes are, and we hope the result is favorable," he said after the commission's enlargement report was published.
Pat Cox, the Irishman who serves as president of the European Parliament, said his compatriots had gained much from EU membership, referring to vast structural funds that have been a shot in the arm to the Irish economy, and had a "powerful responsibility" to others.
He called on them "to understand that 10 candidate states are now calling, and you should use the opportunity in a referendum on Oct. 19 to remove one of the last bricks of the Berlin Wall."