Students from St. Raphael Catholic School in Rockville, Md. stand near a barrier as they await Pope Benedict XVI's arrival to the Papal Nunciature, the Vatican's embassy in Washington, Tuesday, April 15, 2008. (AP

The Pope said yesterday that he felt "profoundly ashamed" by sexual abuse by American priests at the start of his first visit to the United States.

He said on board his plane: "Paedophiles will be completely excluded from the priesthood. It is more important to have good priests than many priests.

"If I read the stories of the victims, I find it difficult to understand how priests can have betrayed their mission to bring holiness in this way, to bring the love of God to children."

Benedict's US tour has been overshadowed by a row over his decision not to visit Boston, the centre of the sexual abuse scandal.

Last year, the Roman Catholic Church had to pay out $615 million (£308 million) in compensation to the thousands of victims, bankrupting six major dioceses, including California.

The Vatican initially said that the issue was "closed" and that the Pope felt he would reopen old wounds by discussing paedophiles. But the Holy See has been forced to reverse its position by several American pressure groups.

One, the Survivors Network of Those Abused by Priests, held a three-hour vigil outside a church in Washington ahead of the Pope's arrival in the capital.

The group said St Dominic's Catholic Church had allowed a known paedophile to remain working for two years. Fr Aaron Cote, 56, was alleged to have molested two young boys in 2004. The church settled a civil suit with their family last year for $1.2 million (£600,000).

The victims of sexual abuse have demanded a meeting with the Pope but are unlikely to get one. "Although the survivors may want a meeting, this is a visit to all Americans," said Mgr Bartholomew Smith, a priest in Washington.