EDINBURGH, Scotland — Pope Benedict XVI, beginning a controversial state visit to Britain, acknowledged today the Catholic Church failed to act decisively or quickly enough to deal with priests who rape and molest children and said the church's top priority now was to help the victims.

The pope's comments to reporters traveling with him from Rome marked his most thorough admission to date of church failures to deal with the sex abuse scandal. The issue has reignited with the recent revelations in Belgium of hundreds of new victims, at least 13 of whom committed suicide.

Benedict also said abusive priests must never have access to children, saying they suffered from an illness that mere "goodwill" couldn't cure.

Benedict's four-day visit to Britain has been overshadowed by anger over the abuse scandal and marked by indifference in the highly secular country where Catholics are a small minority.

The pope's first meeting today was with Queen Elizabeth II, both head of state and head of the Church of England, at a palace in Scotland. Benedict was greeted at the airport by the queen's husband, Prince Philip.

The pope answered questions, submitted in advance by journalists traveling with him to Britain, where anger about the abuse scandal remains high.

Protests are planned, "Pope Nope" T-shirts have been spotted around London and public discussions of the Roman Catholic Church's celibacy requirement for priests are being held.

Benedict acknowledged the opposition, saying Britain had a "great history of anti-Catholicism. But it is also a country with a great history of tolerance."

He was asked about Britain's history of anti-Catholic sentiment and polls that suggest that the faithful had lost trust in the church as a result of the sex abuse scandal. Benedict said he was shocked and saddened upon learning of the scope of the abuse, in part because priests take vows to be Christ's voice upon ordination.

He said he felt "sadness also that the church authority was not sufficiently vigilant and not sufficiently quick and decisive to take the necessary measures" to stop the abuse and prevent it from occurring again. The pope said the victims were the church's top priority now.

He said he expected a warm welcome from Catholics and other believers and "mutual respect and tolerance" among those with anti-Catholic sentiments.

However, thousands of tickets to papal events remained unclaimed.