These two leaders share much common ground, particularly in opposing abortion, gay marriage and embryonic stem cell research. But there are plenty of differences.
They disagree over the war in Iraq, the death penalty and the U.S. trade embargo against Cuba. Benedict also speaks for environmental protection and social welfare in ways that often run counter to Bush policies. And the pontiff told reporters on his plane that he planned to bring up immigration policy with Mr. Bush during their private Oval Office meeting. Benedict has talked forcefully in the past about the damage caused by punitive immigration laws.
Perino said Mr. Bush would focus on areas of agreement, such as on expanding religious tolerance and containing violent extremism. She said shared concerns for Africa and Lebanon would be on the president's agenda.
Perino predicted that Iraq would not "dominate the conversation in any way." If it comes up, it's likely to be focused almost exclusively on the fears of the Christian minority in Muslim-majority Iraq, she said.
Watch live coverage of the Pope's visit to the White House at 10:30 a.m. ET.
Another topic that will get cursory attention, if any, is the clergy sex abuse scandal that continues to devastate the American church. Perino called it not "necessarily on the president's top priorities" for the meeting.
The scandal has cost the church $2 billion in settlements, a moral crisis that became a fiscal crisis. A crisis Benedict is now addressing, reports CBS News correspondent Jeff Glor.
Benedict chose to talk on the topic on his flight to the United States. Answering questions submitted to and selected by Vatican officials in advance, Benedict said he was "deeply ashamed" by the scandal and "will do everything possible to heal this wound."
Aside from holding talks, Mr. Bush has quite a birthday present for Benedict: at least 9,000 excited guests gathered on the White House's South Lawn for a 21-gun salute, a famed soprano's rendition of "The Lord's Prayer" and an emotional presidential welcome.
The pontiff turns 81 on Wednesday, the first full day of his first trip to the United States as leader of the world's Roman Catholics. He'll spend most of the day at the White House, only the second pope to do so and the first in 29 years.
In remarks during pomp-filled festivities that have had Washington aflutter for days, Mr. Bush was to tell the pontiff and the crowd how glad America is to have him visit - and to tell Americans they should listen to his words.
"He will hear from the president that America and the world need to hear his message that God is love, that human life is sacred, that we all must be guided by common moral law, and that we have responsibilities to care for our brothers and sisters in need, at home and across the world," Perino said.
On the way from Rome on Tuesday, Benedict said he was looking forward to meeting a "great people and a great church" during his first papal journey to the United States. The six-day trip to Washington and New York City coincides not just with his birthday, but the three-year anniversary of his ascendance to the Catholic church's top position. Nurturing the U.S. flock is a sensitive and important mission for Benedict at a time not just of ongoing scandal but also of his campaign to tamp down secularism and re-ignite faith.
No pope has been to the United States since the case of a Boston serial molester triggered a crisis that spread throughout the U.S. and beyond in 2002. Benedict's prayer service with U.S. bishops on Wednesday night at the Basilica of the National Shrine of the Immaculate Conception will be watched closely for how he addresses the issue. Because of the prayer service, the pope was not planning to attend a dinner in his honor at the White House.
Mr. Bush has courted the Catholic vote, about a quarter of the U.S. electorate, since his first presidential campaign, with some success. But though Mr. Bush has no more campaigns to run now, he is laying out the red carpet for the pontiff.
The president kicked off the unprecedented series of events byjust outside Washington on Tuesday to meet Benedict's plane, something he's never done for any leader. The pontiff received a screaming, cheering reception befitting a rock star from the hundreds of Catholic students and others who filled bleachers on the tarmac while Mr. Bush, accompanied by his wife, Laura, and daughter Jenna, assumed the unusual role of second fiddle.
Wednesday's South Lawn audience for the pope's arrival, filled out by members of the Knights of Columbus and Boy Scouts and Girl Scouts, is expected to be the largest of Mr. Bush's presidency and among the largest ever at the White House. So many people have been invited, in fact, that many will only be able to see Mr. Bush and Benedict on a large television screen.
Soprano Kathleen Battle has been enlisted to sing "The Lord's Prayer" - a decision the White House defended as appropriate despite the overt insertion of religion into a public event. "I think we've struck the right balance," Perino said. "Many people across America and across the world say that prayer in order to provide themselves comfort and confidence in getting their day started."