Luxembourg (search) voters approved the European Union's proposed constitution in a referendum Sunday, although the EU commissioner said the charter's future remained uncertain following its rejection in France and The Netherlands (search).

Officials said 56.52 percent of the vote was in favor of the constitution, while 43.48 percent voted against it.

Luxembourg is the 13th country to ratify the charter, but rejections by the two larger countries have thrown its future into doubt because it needs unanimous approval to take effect. EU leaders last month agreed to freeze the ratification process, and many observers called into question Luxembourg's decision to proceed with a popular vote.

European Commission President Jose Manuel Barroso said Luxembourg's approval was a "strong signal" that voters still think a constitution can help build "a more democratic Europe."

However, he warned in a statement that its fate remained "uncertain."

Luxembourg Prime Minister Jean-Claude Juncker has said he hopes the referendum will breathe new life into the constitution. He also raised the stakes by saying he would resign if his country voted 'no.'

Luxembourg, a wealthy nation of 450,000 wedged between France, Germany and Belgium, has traditionally been one of the European Union's most ardent supporters.

Many questions remain over the EU's future, including whether it will give full membership to Turkey and whether it should create the posts of EU president and foreign minister.

Juncker's campaign for the charter was bolstered when the tiny country of Malta (search) became the 12th EU nation to ratify the constitution Wednesday by a unanimous parliamentary vote. Luxembourg was the first EU member to go ahead with a referendum following the Dutch and French 'no' votes. Britain, Denmark and Portugal have scrapped theirs.

On Sunday, Juncker dismissed claims that Luxembourg should have canceled its referendum until the future of the constitution is clearer.

"Luxembourg ... has the perfect right to give its view," he said. "If Luxembourg had voted 'no' on May 29, do you think France would have canceled its referendum on June 10?"