Jewish leaders on Friday urged Pope Benedict not to rehabilitate a traditionalist bishop who denies the Holocaust, saying it would foment anti-Semitism and open a deep wound in Christian-Jewish relations.

Italian media have said the pope could this weekend revoke the excommunications of four traditionalist bishops from the Society of Saint Pius X (SSPX) in his latest attempt to heal a 20-year-old schism in the Roman Catholic Church.

The rift became a crisis in 1998, when the late French archbishop Marcel Lefebvre illegally consecrated four bishops in defiance of the late Pope John Paul.

One of the four bishops, the British-born Bishop Richard Williamson, has made a number of statements denying the full extent of the Nazi Holocaust of European Jews, as accepted by most mainstream historians. In comments to Swedish television broadcast on Wednesday, he said: "I believe that the historical evidence is hugely against 6 million having been deliberately gassed in gas chambers as a deliberate policy of Adolf Hitler...I believe there were no gas chambers".

Williamson said he agreed with "revisionists" who say that "between 200,000 and 300,000 Jews perished in Nazi concentration camps, but not one of them by gassing in a gas chamber".

Elan Steinberg, vice president of the American Gathering of Holocaust Survivors and their Descendants, said the possibility that the pope would accept Williamson back into the mainstream church "has been received with shock and consternation".

"For the Jewish people and all persons who feel the pain of the terrible years of the Shoah, this development marks a dangerous blow to interfaith dialogue and encourages hate-mongers everywhere," he said.

Rome's chief rabbi, Riccardo Di Segni, said he was "shocked by such a horror of denial, which is even more grave since it comes from a bishop".

Di Segni told the newspaper La Stampa that Williamson's re-admission into the Church would open "a deep wound in dialogue with Judaism".

The traditionalists bishops reject many reforms of the 1962-1965 Second Vatican Council, notably its decision that Mass should be said in local languages rather than Latin, and its advocacy of dialogue with other religions.

A statement from the traditionalists said the implication they are racist was "entirely false and unjust".

But it said the group had the right to "pray for conversion (of Jews) to the true faith, to study their recent and tragic history, or to question some of their political objectives".

At the end of the Swedish interview, William says he realizes he could go to jail for Holocaust denial in Germany.

Pope Benedict has already made several gestures of reconciliation to the schismatic group, including allowing the unconditional return of the old-style Latin Mass.

That move angered Jews because the ceremony includes a Good Friday prayer for their conversion.