The Pope's planned visit to the Holy Land is to go ahead despite the row over his reinstatement of a Holocaust-denying bishop, Vatican sources claimed today.

The Vatican is expected to confirm by the end of the month that the trip will take place from May 11 to 15, wth the Pope flying first to Amman, in Jordan, and then to Israel. The visit was in doubt not only because of the Holocaust row but also because of the crisis over Gaza, which Vatican officials hope will not flare up again beforehand.

Benedict XVI is to meet a delegation of American Jewish leaders on Thursday to "clear the air" over his lifting of the excommunication of four ultra-traditionalist bishops, including Richard Williamson, who continues to deny that millions of Jews were murdered in the gas chambers. Israel's Minister of Religious Affairs had demanded that the country suspend relations with the Vatican for fostering "Holocaust deniers and anti-Semites".

The papal visit is likely to include a Mass at Nazareth, but it is not clear whether Benedict XVI will pray at the Wailing Wall, as Pope John Paul II did in 2000, or at the Yad Vashem Holocaust memorial in Jerusalem, which contains an exhibit condemning Pius XII, the wartime pontiff, for his failure to speak out against the extermination of Jews in the Nazi Holocaust, or Shoah.

Bishop Williamson last month denied the existence of the gas chambers in an interview with Swedish television, two days before the Pope lifted his excommunication. "I believe there were no gas chambers" he said. "I think that 200,000 to 300,000 Jews perished in Nazi concentration camps but none of them by gas chambers. There was not one Jew killed by the gas chambers. It was all lies, lies, lies."

Last week the Pope instructed Bishop Williamson to renounce his views "in an absolutely unequivocal and public way", saying that otherwise he could be fully readmitted to the Roman Catholic Church. The Vatican said that the Pope had been previously unaware of the bishop's stand.

However, in an interview with the German magazine Der Spiegel Williamson remained defiant, saying that he would have to examine the historical evidence. "It is not about emotions but about historical evidence," he said. "If I find this evidence, I will correct myself. But that will take time. I was convinced that my views were right on the basis of my own research from the 1980s. But now I see that there are many honest and intelligent people who think differently and I therefore must look again at the historical evidence.

He had ordered a book on the "technique" of gas chambers in Auschwitz and would " read and study it".

However Bishop Williamson also defiantly refused to accept the reforms of the Second Vatican Council - which revised and modernised the tenets of modern Roman Catholicism in the 1960s - saying that it had led to "theological chaos".

He said he was astounded by the controversy, and denounced "liberal bishops" for using it to undermine Pope Benedict. "Catholics of the Left" had not yet forgiven the fact that the former Cardinal Joseph Ratzinger had been elected Pope despite his reputation as a theological conservative.

The debacle has caused friction within the Vatican, with many officials blaming Cardinal Dario Castrillon Hoyos, the 79-year-old former head of the Congregation for the Clergy, for advising the Pope to rehabilitate the followers of the late renegade archbishop Marcel Lefebvre while failing to foresee the blazing row which would ensue.

Father Federico Lombardi, the papal spokesman, admitted that the order for Bishop Williamson to recant should have been issued a the same time as the announcement of the excommunications being lifted. "One thing that is certain is that the Pope did not know," he said. "If someone should have known, it was Cardinal Castrillon Hoyos."

In another glimpse into the behind-the-scenes row over the fallout of the Williamson affair, Cardinal Walter Kasper, the Vatican official responsible for relations with Jews, said that he had not even been consulted. He said that "in the Vatican this topic was talked about too little and it was never verified where the problems might emerge. I would have hoped for more communication beforehand".