By Tom Heneghan, Religion Editor
PARIS (Reuters) - Chancellor Angela Merkel urged Germany's Protestant and Roman Catholic churches on Monday to stress their common beliefs at ceremonies marking the 500th anniversary of the start of the Protestant Reformation.
Although still five years away, the date has already prompted debate between Protestants preparing major celebrations and Catholics who rue the rebellion of the German monk Martin Luther in 1517 as the start of a painful split in western Christianity.
The Evangelical Church in Germany (EKD), the country's largest association of Protestant churches, wants the Catholics to attend its planned "Luther Jubilee", and its annual synod in a Baltic resort near Luebeck is debating how to make it possible for them to do so.
Merkel, daughter of a Protestant pastor, made a rare visit to the synod and said that, in a secularized world, Christian churches should stress what united them, rather than their enduring theological differences.
"I've learned that even the word 'jubilee' used in connection with the Reformation can give rise to discussions," Merkel said. Catholics attach a special meaning to 'jubilee years' and would prefer to call the event a commemoration.
"Especially in a very secular world, we should always stress what is common in the Christian religion," she said.
The Reformation began in 1517 when Luther nailed his 95 Theses to a church door in Wittenberg to denounce corruption in the Catholic Church, especially the sale of indulgences to help build the lavish Saint Peter's Basilica in Rome.
Excommunicated by Rome, he won support from German princes who soon battled others who remained Catholic. The ensuing wars of religion killed about a third of Germany's population over the next century and spread to neighboring countries as well.
The two churches are roughly equal in size in Germany and, despite falling attendances, both run many schools and social services. Intermarriage is common.
EKD President Nikolaus Schneider told the synod the two churches had already agreed to write a joint book on Christianity next year and hold a major conference on the Bible in 2015 in preparation for the anniversary.
They have also begun discussing whether they could hold a joint service of reconciliation in 2017 "that recognizes before God all the injuries both churches inflicted on each other".
Speaking for the Catholic Church, Hamburg Archbishop Werner Thissen told the synod he hoped for an agreement on how to mark the anniversary.
"Times have changed dramatically since Luther," he said, noting that the Catholic Church's modernizing Second Vatican Council of 1962-65 had "learned a lot from Martin Luther".
(Reporting By Tom Heneghan)