Afterward, the Vatican said the leaders discussed immigration, the Middle East peace process and aid to developing nations. But the Vatican's statement also underscored the pair's deep disagreement on abortion.

"In the course of their cordial exchanges, the conversation turned first of all to questions which are in the interest of all and which constitute a great challenge ... such as the defense and promotion of life and the right to abide by one's conscience," the statement said.

Obama and Benedict had spoken by phone but had not met before.

Benedict asked Obama about the G-8 summit, eliciting Obama's assessment that it was "very productive."

The cameras clattered while they sat down at the pope's desk.

"Your Holiness, I'm sure you're used to having your picture taken. I'm getting used to it," Obama said.

Later in the day, Obama flew to Ghana on his first trip to sub-Saharan Africa as president, but second visit to Africa. He gave a speech in Egypt last month.

He landed in Ghana soon after 9 p.m. local time and met a long line of dignitaries, led by President John Atta Mills. An ethnic African group danced and banged drums for Obama's arrival. Obama will make a speech to lawmakers there and tour an oceanfront fort once used to ship slaves to the Americas. Obama, joined by his wife and two daughters, will be in Ghana less than 24 hours.