The uproar is loudest in France, where clergy and laity are ringing alarm bells against bringing back the old liturgy.

Church leaders in Belgium and Germany have also grumbled, saying demand for the old Tridentine mass in Latin was minimal and warning the traditionalists could use it as a wedge to smuggle more divisive issues into the world's largest church.

"The (Tridentine Latin) rite is only the locomotive -- the issue is the carriages that are pulled behind it," Brussels Cardinal Godfried Danneels said last week. "Behind this locomotive are carriages that I don't want."

These rumblings hint that Benedict might alienate many mainstream Catholics if he opts for a deal to heal an 18-year schism with the Society of Saint Pius X, a Swiss-based group that rejects the landmark Second Vatican Council (1962-1965).

"We risk creating a front of sadness, discouragement and disappointment with the Holy See," said Toulouse Archbishop Robert Le Gall, using the Vatican's official name. "The liturgy is just the tip of the iceberg."

SIGN OF STEP BACK

The Tridentine mass is seen as a symbol of rejecting modernizing reforms such as more participation by the faithful, respect for Judaism and cooperation with Protestants.

Most of the world's 1.1 billion Roman Catholics attend Sunday or daily mass in their own language rather than Latin which Vatican II sidelined. Many agree with the respect for other religions that Vatican II made official Church policy.

Priests can still say mass in Latin. All they need is permission from their bishop.

But in fact, few Latin masses are said and few faithful turn out for them, the German bishops conference noted last month after conducting an internal study. "We could not see any growth in interest in it, as some have asserted," they added.

The Society of Saint Pius X, which has about 1 million followers worldwide and is especially strong in France, does not just champion the solemn old Latin mass but flatly rejects what founder, late French Archbishop Marcel Lefebvre, called "neo-modernist and neo-Protestant" reforms of Vatican II.

Benedict shares their love of Latin and the traditional liturgy and seems keen to bring them back into the fold so they don't set up a permanent parallel Catholic-like church.

Reports from the Vatican say he is also ready to meet their main demands -- which are the unconditional revival of the Tridentine mass as an alternative to the modern liturgy and the lifting of excommunications of the four SSPX bishops whom Lefebvre consecrated in defiance of the Vatican in 1988.

A "LOYAL OPPOSITION"?

Paris Archbishop Andre Vingt-Trois bluntly spelled out the problems the traditionalists would bring at a Paris conference attended by Cardinal Francis Arinze, the Vatican official in charge of liturgical issues such as how to say mass.

"Under the cover of a campaign to defend a certain type of liturgy, there is a radical critique of the Vatican Council, even outright rejection of some of its declarations," he said.

"The rejection of new liturgies was followed by public insults against the popes and crowned by violent acts such as the forcible seizure of a parish church in Paris and an aborted attempt by the same people to repeat this," he said.

The warning from Vingt-Trois came after a rising chorus of criticism from other clergy in France, where the schism also has strong political overtones because of the links some SSPX followers have with royalist or far-right movements.

In an open letter, 30 young priests said Benedict, 79, should encourage them "to work in the world as it is ... rather than plunge us back into the liturgical life of another age."

Besancon's Bishop Andre Lacrampe said he would like to welcome traditionalists back into the Church but not in a quick deal that avoided answering the Vatican II question.

Danneels, an outspoken moderate in the overwhelmingly conservative College of Cardinals, urged the Vatican to be tough in its negotiations with SSPX.

"I've never heard their leaders say even once that they accept Vatican II," he told the Brussels daily De Standaard.

"I think the Vatican should demand this."