By Philip Pullella
VATICAN CITY (Reuters) - The Vatican began talks on Monday with an ultra-traditionalist Catholic splinter group, one of whose bishops has denied the full extent of the Holocaust, with the aim of re-integrating it fully into the Church.
Vatican officials and leaders of the Society of Saint Pius X (SSPX) discussed what a statement called "doctrinal differences still outstanding" between the group and Rome.
The traditionalists reject many of the reforms of the 1962-1965 Second Vatican Council, which modernised many aspects of the 1.1 billion member Church, including its liturgy, its relations with other Christians and its view of Jews.
The group, numbering several hundred thousand members, insists that it represents the true faith, and opposes the way the Church has evolved over the past 40 years.
The SSPX says the Vatican and the vast majority of the Church went off the rails at the Council.
The Vatican rejects this stark view but Pope Benedict wants to try to bring the traditionalists back into the fold and heal a schism that began some 20 years ago.
The two sides, far apart on many issues, will meet every two weeks and the negotiations could last months, if not years.
Earlier this month, one SSPX leader, Bishop Bernard Fellay, said bluntly: "The solution to the crisis (in the Church) is a return to the past."
One of the Council's major documents, "Nostra Aetate" (In Our Times) repudiated the concept of collective Jewish guilt for Christ's death and urged dialogue with all major religions.
Last January the group was put in the international spotlight after the pope, trying to start the process of bringing it back into the fold, lifted the excommunications of four of its bishops.
One, Richard Williamson, caused an international furore by denying the full extent of the Holocaust and stating that there were no gas chambers.
Jews have pointed to comments by SSPX leaders, including one by Rev. Franz Schmidberger who said Jews would be "complicit in deicide" -- the killing of God -- until they rejected "their forefathers' guilt" by accepting Christ and being baptised.
In a statement, the American Gathering of Holocaust Survivors and their Descendants urged the Vatican to remember the "poisonous atmosphere" in Catholic-Jewish relations before the Second Vatican Council, an atmosphere which many Jews believe contributed to allowing the Holocaust to take place.
They called on the pope not to let the talks "trivialise the memory" of Holocaust victims by giving in too much to a group they see as anti-Semitic and which critics say wants to turn the clock back on 40 years of progress in inter-religious dialogue.
(Editing by Tim Pearce)