Pope Francis is due to step onto African soil for the first time to address the continent's fast-growing Catholic congregation during a trip that will test his ability to bridge faultlines between Christians and Muslims.
The six-day tour will start in Kenya and Uganda, which have both seen Islamist militant attacks, before he travels to the Central African Republic, a nation torn by Muslim-Christian strife.
He is due to arrive in Nairobi at about 1400 GMT on Wednesday (0100 AEDT Thursday).
"We are living at a time when religious believers, and persons of goodwill everywhere are called to foster mutual understanding and respect, and to support each other as members of our one human family," the pope said in a pre-trip message.
Millions of Christians - Catholics and others - are expected to turn out in welcome and for public celebrations of Mass, presenting a challenge for national security forces.
Africa's Catholic church is growing fast with an estimated 200 million adherents in 2012, which could rise to half a billion in 2050.
"We are ready to receive him," Kenya's inspector general of police, Joseph Boinnet, said.
"Security arrangements have been put in place, right from arrival."
He did not say how many police would be deployed in the capital for the visit, which includes Mass at the University of Nairobi on Thursday but media sources indicate 10,000 officers would be involved.
Kenya has been targeted by Somalia's Islamist group al Shabaab in the past two years with hundreds of people killed, including 67 during an assault by al Shabaab gunmen on a Nairobi shopping mall.
He will also seek to heal ethnic rifts that have long plagued Kenya.
"Pope Francis' visit to Kenya will be focused on inclusivity and reconciliation in relation to ethnic and religious tolerance, peace and stability," Kenyan presidential spokesman Manoah Esipisu said.
The pope will visit the Nairobi headquarters of the United Nations on Thursday.
He will also hold Mass on Saturday in Uganda, with 12,000 police to be deployed.
Potentially the most hazardous stop of his trip is the third leg to the Central African Republic, where dozens have died since September in violence between Muslim Seleka rebels and Christian anti-balaka militias.
In the capital, Bangui, he will visit a mosque in one of the most dangerous districts.
