Luxembourg -- Luxembourg's Grand Duke Henri, widely seen as a modernizing figure but strongly attached to Roman Catholic values, is set to see his sovereign powers clipped in a furor over euthanasia.

The 53-year-old sovereign threw off his traditional political neutrality when he let it be known that, for "reasons of conscience," he would refuse to sign into law a bill adopted by parliament to legalize euthanasia.

In doing so, he triggered a proposed constitutional amendment -- swiftly promoted by Prime Minister Jean-Claude Juncker -- towards a purely formal Swedish style of monarchy in the small but wealthy duchy.

A fresh-faced father of five related to the Belgian and Swedish royal families, Grand Duke Henri has adopted a more modern style than his predecessors, building a strong bond with his people.

In this largely Catholic nation of 480,000 that boasts the highest per capita GDP of any EU member state, his stance against euthanasia is unlikely to upset that bond, even if it ends up trimming his powers.

A graduate of Britain's Sandhurst military academy and Geneva University, his strong adhesion to Catholic and family values is shared by his Cuban-born wife, Grand Duchess Maria Teresa.

"It is well-known that the grand duchess is close to the charismatic movement which has radical positions on matters such as euthanasia," said Liberal deputy Eugene Berger.

"And we know that the grand duchess has a great influence over the grand duke," added Berger, one of the few Luxembourg politicians to talk openly on the subject.

"I understand the grand duke's problems of conscience," Prime Minister Juncker said Tuesday when he announced plans to change the constitution so that the grand duke would merely sign laws into being, rather than approve them.

"But I believe that if the parliament votes in a law, it must be brought into force," he said.

Changing the constitution will require a two-thirds majority in parliament -- something that Juncker, 53, the longest-serving head of government in the European Union, is likely to have had assured before his announcement.

The Luxembourg constitution, closely modeled on Belgium's, makes the grand duke not just a symbol of the picturesque landlocked country's identity, but also the guarantor of its institutions.

While sitting above the political fray, he nevertheless wields "a moral authority which confers an influential power," the Grand Duchy's website explains.

The system of a sovereign "reigning but not governing" has worked without any problems for almost a century -- giving Luxembourg a high degree of stability appreciated by the many global investment funds that it hosts.

Luxembourg's last constitutional crisis arose in 1919 when Grand Duchess Marie Adelaide was forced to abdicate amid accusations of Catholic bias and suspicions of German affiliations during World War I.

Until now, Grand Duke Henri, and his late father grand duke Jean, only strayed from their neutral stance in consensual matters, such as defense of the environment.

But for several months he has let it be known, though never publicly, that he would not approve legislation to allow euthanasia and assisted suicide -- which it now is likely to turn up on his desk in the spring of 2009.

During its first parliamentary reading in February, the legislation was narrowly approved by a vote of 30 in favour and 26 against.

That vote was a defeat for Juncker's own Christian Social People's Party, whose members strongly opposed the move, fearing it would make euthanasia an everyday event.

It was approved thanks to support from Socialist deputies within the coalition government, along with opposition Liberals and Greens.

AFP/Expatica