Chief Executive Thomas Enders said the euro has now "crossed the pain threshold." The rate of the dollar's fall "is life threatening," he was quoted by Der Spiegel magazine as saying Thursday.
Still, the stronger euro confers benefits as well, holding down energy prices and inflation. And its strength reflects rising confidence in the euro zone and the global prospects of an economically unified Europe.
"There is a renewed self confidence on the European continent," said Holger Schmieding, chief European economist at Bank of America.
"A strong euro shows that people around the world think that the euro economy isn't as weak as they once thought. And it shows that people think the ECB is doing a good job."
Such pride may be behind the rethink by the skeptical Danes and Poles, whose leaders announced this week they might be ready for the euro.
Danish Prime Minister Anders Fogh Rasmussen, whose country rejected the euro in 2000, said Thursday he plans to hold another vote, saying "a lot has changed."
Poland's new prime minister pledged Friday to put the country on the path to quickly adopting the euro. His country is one of five EU newcomers who chose not to align its currency with the euro in an exchange rate mechanism.
"In terms of sentiment, it's positive if an extremely euroskeptic country changes its mind," said Paul Mackel, a currency strategist at HSBC in London.
"That would send a positive message to pro-euro officials in other countries."
The euro entered circulation in 12 EU countries in 2002. At the time, Denmark, Britain and Sweden were the only EU members to stay outside.
After the bloc expanded in 2004, Slovenia has adopted the currency, while Cyprus and Malta will start using the euro on Jan 1, 2008.
In Cyprus, officials are taking a risky bet in their enthusiasm to celebrate the island nation's adoption of the single currency.
At official holiday celebrations this year, Santa is taking a backseat and being replaced by Europa — much to the ire of locals. A character in Greek mythology, Zeus named the continent after her out of gratitude that she bore him three sons.
"Where did (Europa) come from? You can't mess with Santa Claus," said 40-year-old Zena Georgiou, a mother of two daughters aged 3 and 6.
Associated Press writers Menelaos Hadjicostsi in Nicosia, Elizabeth Ryan and Angela Charlton contributed to this report.