Madeleine McCann's parents, Kate and Gerry McCann, both Catholics, are expected to attend a general audience at the Vatican on Wednesday to discuss the disappearance of their daughter.
The parents have said they hoped to draw profound strength from any audience as well as helping to publicise the campaign to bring Madeleine home.
"Under normal circumstances we would be extremely excited about meeting the Pope, but as we are here as a result of Madeleine's abduction the circumstances are very different," Gerry McCann wrote on his web log.
"We expect to receive a great spiritual lift, especially if we get to speak to the Pontiff personally."
A spokesman for Cardinal Cormac Murphy-O'Connor, who is helping to arrange their visit, said: "The cardinal is conscious of the prayers of the entire Catholic community in this country for the McCann family at this distressing time.
"Having spoken to Dr Gerry McCann, the cardinal is facilitating the presence of the McCanns at an audience with the Holy Father as soon as is feasible."
The McCanns said the trip would also be difficult as they will leave behind their two other children, two-year-old twins Sean and Amelie, with relatives in Portugal.
After meeting the Pope, the couple will hold a news conference and hand out missing posters of Madeleine in Italian.
On Tuesday they released the last video footage of their daughter taken before her disappearance on 3 May from her family's holiday apartment in the southern Algarve region of Portugal. She vanished after her parents left her and her siblings alone in their room while they went to a nearby tapas bar inside their hotel complex.
