5 MIN. DE LECTURA
* Pope making first trip to Africa
* Stop in Central African Republic still in doubt
* Growing fault line between Christians and Muslims on continent
By Philip Pullella
VATICAN CITY, Nov 23 (Reuters) - Pope Francis' first Africa trip will highlight the problems of building dialogue between Christianity and Islam as both religions grow fast on the continent, threatening to widen an already volatile fault line there between them.
The three countries on the pope's Nov. 25-30 itinerary - Kenya, Uganda and the Central African Republic - have been scarred by radical Islamist attacks or Muslim-Christian sectarian strife and security concerns have meant the trip has been kept relatively short.
With the backdrop, too, of the bloody attacks by Islamist militants in France and Mali, the pope's top advisers readily acknowledge the difficulties of conducting dialogue between Catholics and other Christian churches and Muslims.
"How can you dialogue with this mentality? ... There is no dialogue with extremists. Look at what they do," said Cardinal Robert Sarah, who is from Guinea in West Africa and one of the highest-ranking African officials at the Vatican.
Bishops in Sudan, which for decades was divided between the mostly Muslim north and the south where there are many Christians, have often said Christians there are considered "less than a dog ... firewood to be a burned", said Sarah, speaking in Rome on Friday.
Francis has sought to heal relations between the faiths by saying that Christians would be wrong to equate Islam with violence. But the potential for collision between the two dominant faiths in sub-Saharan Africa is expected to increase along with the population in coming decades.
Christianity and Islam in the Sub-Saharan region are both expected to have more than twice as many adherents in 2050 as they did in 2010, according to a study this year by the Pew Research Center on Religion and Public life.
Christianity is projected to remain the region's largest religious group, up from 517 million adherents in 2010 to more than 1.1 billion in 2050. The Muslim population is expected to grow at a faster rate, rising from 248 million to 670 million, it said.
According to a study by the Center for Applied Research in the Apostolate (CARA) at Georgetown University, the number of Catholics in all of Africa could more than double to 460 million by 2040.
Security concerns mean the pope's movements will be confined to the capitals. All the same, the Vatican says he will for the most part travel in an open popemobile or a small car, eschewing bulletproof vehicles. A spokesman denied a report that Francis would wear a bulletproof vest.
Kenya, his first stop, has seen some of the worst violence. Two years ago, gunmen from the Somali militant group al Shabaab massacred at least 67 people inside Nairobi's Westgate shopping mall and held out for four days as security forces laid siege to the complex.
In Uganda, al Shabaab bombed sports bars where people were watching soccer's World Cup on television in 2010.
But potentially his most hazardous stop is Nov. 28-29 in Bangui, capital of the Central African Republic, where dozens of people have been killed since September in violence between Muslim Seleka rebels and Christian anti-balaka militias.
His trip is scheduled to include a visit to a mosque in one of Bangui's most dangerous districts. French officials have hinted heavily that the Vatican should consider scrapping the Bangui leg of his trip or at least scaling it back.
"We've informed the Vatican authorities that Pope Francis' visit carries risks for himself and for hundreds of thousands of believers who could be there to see him," a French defence ministry source said in Paris.
The Vatican's security chief returned to Bangui for a re-assessment last week and some Vatican officials say the visit might be reduced to a "touch and go" stop at the airport.
But that would deny the pope the possibility of making a stop at the mosque to condemn violence in God's name.
Last year, on his way back from Turkey, Francis said automatically equating Islam with violence was wrong, but he called on Muslim leaders to issue a global condemnation of terrorism to help dispel the stereotype.
Catholic relations with Islam hit a low point in 2006 when Francis' predecessor, Benedict XVI, caused storms of protest throughout the Islamic world when he made a speech that suggested to many Muslims that he believed Islam espoused violence. Benedict said he had been misunderstood and apologised. (Additional reporting by Edmund Blair in Nairobi, Marine Pannetier in Paris and Crispin Dembassa-Kette in Bangui; Editing by Richard Balmforth)