European Union leaders put a brave face Monday on Sweden's rejection of the euro, but could not hide their disappointment at the sharp slap for a key project of the increasingly integrated bloc.

The British government, battling to persuade a distinctly euro-sceptic public, downplayed the significance of the crushing failure in Sweden, while its own "no" campaigners openly crowed.

German Chancellor Gerhard Schroeder lamented the Swedish decision, but insisted he remains confident the euro -- currently shared by 12 EU states -- can eventually be accepted more widely.

"The door was not closed and the possibility of Sweden adopting the euro in the future remained intact," he said, while adding that he respected "the sovereign decision by the Swedish citizens."

In Brussels the European Commission, the EU's executive arm, also sought to accentuate the positive.

Commission President Romano Prodi said the Swedish government's failure to convince its people was due to natural caution. "It didn't succeed due to fear of the new among public opinion," he told the Italian daily La Repubblica.

Italian Foreign Minister Franco Frattini, whose country currently holds the EU'S rotating presidency, said the Swedish people's choice must be respected, but said efforts to eventually get Sweden to join the euro should continue.

"We must continue to work at ensuring the Swedish project does not end," he said. "We must work to convince (Swedish) citizens that Europe is a great opportunity and that there is no risk of loss of identity," he said.

Taking note of Sweden's decision, France, which has fuelled criticism of the single currency project by giving greater priority to boosting its own economy than to meeting euro-zone rules, said the euro area would welcome any EU state that wished to join.

"The euro zone remains open to all European Union member states that wish (to join) and fulfill conditions set in the treaties," French Foreign Ministry spokesman Herve Ladsous said.

Analysts said the failure of EU heavyweights like France to stick to the rules may well have been a factor in the decisiveness of the Swedish vote.

In London the Foreign Office sought to shrug off the results of the referendum, in which 56 percent of Swedes rejected the euro while only 42 percent voted "yes" to the single currency.

"The Sweden referendum doesn't affect the position of the United Kingdom because our position is very clear that the national economic interests would be the determining factor," said a spokesman.

The decisive Swedish "no" vote also does not augur well for hopes of convincing Denmark, another European Union member still outside the euro zone, to accept the currency which has been legal tender in 12 states since 2002.

Sweden is the first country to reject the euro since the single currency began circulating as cash in January 2002, and the result is expected to have repercussions elsewhere in Europe.

Britain, Sweden and Denmark are the only members of the European Union who have not joined the euro zone. The British public remains largely hostile to adopting the single currency.

Danish Prime Minister Anders Fogh Rasmussen, who aims to lead his country into the eurozone, insisted the Swedish vote had "no bearing on our attitude towards the single currency."

Spanish Foreign Minister Ana Palacio said she deeply regretted Sweden's decision, calling it "bad news for Europe and bad news for Sweden."

Some European newspapers saw the Swedish vote as a further rejection of the EU's ruling classes.

The vote is "a rebellion by the Swedes against their political and economic elite ... It may accelerate the drift towards a multi-speed Europe and heralds more difficulties ahead," said the centre-left Spanish daily El Pais.

Britain's eurosceptics appeared among the biggest winners from the Swedish "no" vote, which was bigger than expected given the murder last week of pro-euro foreign minister Anna Lindh.

"(The result) highlights the huge difficulty that the government would have winning a vote in Britain, where opposition is even higher," said George Eustice, director of the "no" campaign against British membership of the euro.