Next comes the audience with the pope, whose generally conservative views will not entirely mesh with Obama's. They are likely to discuss world poverty, the Middle East and other topics, aides say, but the visit will be largely personal and spiritual.

"There are issues on which they'll agree, issues on which they'll disagree and issues on which they'll agree to continue to work on going forward," White House national security adviser Denis McDonough told reporters Thursday.

"Given the influence of the Catholic Church globally," he said, and "the influence of the Catholic Church and church social teaching on the president himself, he recognizes that this is much more than your typical state visit."

Obama is a Protestant seeking a new church in Washington.

He will become the third straight US president to visit Ghana, a relatively stable democracy in a continent wracked by poverty and heavy-handed governments. But he is the first such president of African descent.

Obama chose Ghana, Gavin said, "because it's such an admirable example of strong, democratic governance, vibrant civil society." There's much to admire, she said, and to hold up as "a counter to what one often hears about Africa."

On Saturday, Obama will meet with Ghana's president, John Atta Mills, and address the nation's parliament.