Plans are being finalised for Pope Benedict XVI to visit Israel in May next year, the Vatican has confirmed.

The Pope had intended to make the announcement himself at Christmas, Vatican sources said. However the news was leaked this week by the Israeli daily Haaretz. Father Federico Lombardi, the Vatican spokesman, said diplomatic contacts were under way to prepare a trip, and the Israeli Ambassador to the Holy See, Mordechay Lewy, said the visit was ''very probable''.

Mr Lewy added that ''a visit by the pope to the Holy Land would have incomparable historic value and he himself has already announced his desire to go there".

Israel and the Vatican have only had full diplomatic relations since 1993. There remain a number of unresolved issues, including the Vatican's request for custody of Christian sites in Israel such as the room of the Last Supper on Mount Zion and a church in Caesaria linked to St Peter. The Vatican is also seeking tax exemptions for Church property in Israel.

The most recent cause of tension however is the controversy surrounding the Vatican's plans to beatify Pius XII, the wartime pontiff whom many Jews criticise for his alleged failure to speak out against the Nazi Holocaust. In October, the Israeli Social Affairs Minister, Yitzhak Herzog, said plans to beatify Pius XII - the step before sainthood - were ''unacceptable''.

The Vatican, for its part, objects to an exhibit at the Yad Vashem Holocaust Museum in Jerusalem which accuses Pius XII of silence in the face of Nazi persecution of the Jews. Mr Lewy said it was too early to say whether Benedict would visit the museum, adding that ''dates and details have not been fixed''. Pope Benedict has vigorously defended Pius XII, but has not yet approved his beatification or announced a date for the ceremony.

John Paul II made an historic trip to Israel as part of a Holy Land tour in 2000, and Pope Paul VI made a brief visit there in 1964.