The Pope has said he was "deeply ashamed" by sexual abuse commited by Catholic priests in the US and vowed to keep paedophiles out of the clergy, as he began his first visit to the US as pontiff.
Benedict XVI will hold talks with George Bush during the six-day trip and also pray at New York's World Trade Center and address the UN.
"We are deeply ashamed and will do whatever is possible so that this does not happen in the future," he said on a plane to the US on Tuesday.
The trip is the first by a pontiff since a wave of abuse scandals began in 2002, provoking legal actions that led to more than $2 billion in settlements.
Benedict said the Catholic Church would do everything possible to screen candidates for the priesthood "so that only really sound persons can be admitted".
"It is more important to have good priests than to have many priests," said the pontiff, who will be greeted upon arrival at Andrews Air Force Base in the state of Maryland, by George Bush, the US president.
Priesthood in decline
The two have disagreed on a number of issues, most notably over the war in Iraq and the US embargo of Cuba, but have found common ground in opposing abortion, gay marriage and stem cell research.
Dana Perino, a White House spokesman, said ahead of the visit that talks between the two were likely to be "frank and open".
Perino said: "They can have very frank and open disussions with one another, but I think that their shared values are stronger than any disagreements on policy that they may have."
A poll released this month by the Pew Forum on Religion & Public Life showed the German-born pope was viewed favourably by most peole in the US, but was not as popular as his predecessor John Paul II.
But Benedict's visit also comes amid concerns over a decline in the numbers of people in the US joining the priesthood.
A recent Catholic University study found that 17 per cent of the priests serving in American churches come from other countries.
Enrollment in the four-year theology programs required to join the priesthood have not risen for a decade, the New York Times reported.