President Bush arrived at the Vatican this morning to a welcome from Pope Benedict XVI so unusually cordial that it gave rise to speculation in the Italian press that Mr Bush might convert to Catholicism.

In an unprecedented move the pontiff met Mr Bush for their final encounter not in the papal library, as is usual under normally strict Vatican protocol, but at St John's Tower, a restored medieval tower in the Vatican walls used to house the Vatican's VIP guests.

As he entered the tower with the Pope, Mr Bush repeatedly exclaimed, "this is such an honour, such an honour".

Mr Bush and the Pope held talks for half an hour, after which they gave each other photographs commemorating the Pope's visit to the White House in April, leading Laura Bush to laugh and exclaim, "We're giving the same things!" Earlier Mrs Bush greeted the Pope by saying, "How are you, so good to see you, you look great." Mr Bush alternately addressed the Pope as "Your Holiness" and "Sir" observing "You've got a beautiful place here."

As Mr Bush and the Pope posed for photographs flanked by Mrs Bush and Mary Ann Glendon, the US Ambassador to the Holy See, Mr Bush joked to the pontiff, "We are surrounded by impressive women."

A communique issued by the Vatican said that Mr Bush and the Pope discussed US-European relations, the Middle East and peace efforts in the Holy Land, and globalisation and the world food crisis.

The talks were followed by a stroll around the Vatican gardens and a performance by the Sistine Chapel choir of two motets, one by Palestrina and the other a modern composition by the choir's conductor, Giuseppe Liberto.

In another unusual gesture the Vatican distributed to journalists a minute-by-minute programme with a cover photograph of St John's Tower and the Vatican gardens, to underline the exceptional nature of the visit. Mr Bush arrived in a convoy of some 50 vehicles, accompanied by his wife Laura and Mrs Glendon.

The Vatican said that the Pope simply wanted to show his appreciation for the hospitality he was shown on a recent visit to the US. However Marco Politi, the veteran Vatican correspondent of La Repubblica, said that Mr Bush's unstinting admiration for the Pope had given rise to talk of the President's possible conversion, by analogy with Tony Blair. Mr Bush is a Methodist and a "born again" evangelical Christian.

Vatican sources said that no conversion process was under way, and could in any case only take place — as in the case of Mr Blair — once Mr Bush had left office. They said that the rumours appeared to arise in part from remarks by Nancy Brinker, the White House head of protocol, who had said that Mr Bush was "a huge fan of this Pope", had "total respect" for the pontiff and "totally supported" him.

However both Vatican and US officials said that this referred to the fact that despite their differences on Iraq and the Middle East, Mr Bush and Pope Benedict saw eye to eye on the need to defend Christian values in the West and on specific issues such as abortion, gay marriage and stem cell research as well as poverty in Africa.

Corriere della Sera noted that differences between the Vatican and Washington over Iraq now "lie in the past", with the Pope's concerns focused more on Iraq's transition to democracy and the plight of Christians in Iraq and the Arab world.

After his Vatican visit Mr Bush flies to Paris, where he will outline a vision of transatlantic unity which he hopes his successor next January will fulfil.

"I see a commitment to a powerful and purposeful Europe that advances the values of liberty within its borders and beyond," Mr Bush will say in a speech in Paris. "And when the time comes to welcome a new American president next January, I will be pleased to report to him that the relationship between the United States and Europe is the broadest and most vibrant it has ever been."

He will add, according to the White House: "We must go forward with unity ... Dividing democracies is one of our enemies' goals and they must not be allowed to succeed."

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