Pope Benedict and President George W Bush disagree on the Iraq war and other foreign policy issues, but their White House meeting this week may focus more on areas of agreement like abortion.
The Vatican strongly opposed the Iraq war which it believed did not follow the Catholic "just war" doctrine which justifies defensive conflicts but not preemptive attacks, analysts say.
Bush argued that the US-invasion of Iraq in 2003 was necessary to remove a threat from Saddam Hussein and help spread democracy in the Middle East.
The war will likely come up in the talks but no public statement is expected because the Pope usually avoids conflict with leaders of countries he visits. Pope Benedict has been deeply concerned about the Iraq situation, especially the plight of minority Christians and the death of a Chaldean archbishop who was kidnapped by gunmen.
"From the beginning the Vatican had serious concerns about the appropriateness of the war," said Stephen Schneck, a political scientist at Catholic University.
In other foreign policy differences, the Vatican has diplomatic relations with Cuba, supports dialogue with Iran and Syria and is more enthusiastic about working through the United Nations and other international bodies.
"The Vatican's approach is you should talk to everybody, talking never hurts you. And you try and find peaceful solutions to these problems," said Rev Thomas Reese, a Georgetown University theologian. "The Vatican has always been a strong supporter of the United Nations, of multilateral, multinational approaches to problems."
Both seek an Israeli-Palestinian settlement. Bush is pushing for an agreement in his last year in office, having visited Israel and the West Bank for the first time as president.
The two men present contrasting personalities and management styles.
