Pope Benedict XVI has raised expectations he will apologize directly to victims of past clergy sexual abuse while he is in Australia this week for a Roman Catholic gathering of hundreds of thousands of pilgrims.

The leader of the church told reporters during a 20-hour flight to Australia for a nine-day visit starting Sunday that he would do everything possible to achieve "healing and reconciliation with the victims" of maltreatment by priests.

Activists in Australia, who have demanded the pontiff make a formal apology to victims to help cool the scandal that has dogged the church in recent years, cautiously welcomed his comments. Still, they said he should go further and stop the church's opposition to compensation claims.

Senior clerics organizing the World Youth Day festival in Sydney this week have avoided using the word "apology" to describe remarks Benedict is expected to make about the problem of clergy abuse, but they have made clear there will be some expression of regret.

Benedict touched down Sunday at a military air base on the outskirts of Sydney, where there is a growing buzz about the festival as pilgrims flood into the city for the largest public event since the 2000 Olympic Games.

He was greeted on the tarmac by Prime Minister Kevin Rudd and other government and church officials, although Sunday's arrival was relatively low-key, with crowds kept away from the base.

The pontiff was then whisked by motorcade to a retreat in the city where he will stay out of the public eye until Thursday, when he will ride by boat through Sydney harbor to a wharf-side venue and address a large crowd.

Aides say the 81-year-old pontiff is in good health, though his schedule has been arranged to include a few days of rest before attending the World Youth Day events, which start Tuesday. The festival will culminate on July 20 with an open-air papal Mass at a racetrack in Sydney.

During the flight from the Vatican, Benedict told reporters he would work for "healing and reconciliation with the victims" of sexual abuse by Roman Catholic clergy in Australia "just as I did in the United States."

At the start of a U.S. visit earlier this year, Benedict said he was "deeply ashamed" of the abuse scandal and pledged to work to make sure pedophiles do not become priests. He held a private meeting with a group of abuse victims.

Bernard Barrett, a spokesman for the victims' group Broken Rites, said Benedict's comments did not go far enough.

"He made some general remarks about regret to reporters and that's not good enough," he told Australian Broadcasting Corp. radio. "We want action, not words."

"The pope must apologize for the way his Australian bishops have covered up sexual abuse, the pope must tell his Australian bishops to stop blocking victims' access to justice in the civil law courts," he said.

Bishop Anthony Fisher, a spokesman for the event in Sydney, said the church in Australia welcomed "the Holy Father's word of compassion and of leadership for us with respect to the victims of sexual abuse."

"Given our efforts to do the right thing in this very difficult area, we're heartened by the Holy Father's words and we look forward to hearing what he has to say" during World Youth Day, Fisher told reporters.

Benedict also signaled he would speak about global warming during his Sydney visit because it was an issue of concern to young people.

The pope said there is a need to "wake up consciences" about the issue.

"We have to give impulse to rediscovering our responsibility and to finding an ethical way to change our way of life," he said. Politicians and experts must be "capable of responding to the great ecological challenge and to be up to the task of this challenge," he added.

In the southern city of Melbourne, more than 100 people, some wearing shirts with slogans such as "Pope is wrong, put a condom on," protested Sunday against World Youth Day and the Catholic church's attitude toward homosexuals, contraception and other issues. A similar demonstration is planned for Sydney next weekend.

Benedict is to be greeted at Sydney Harbor on Thursday by a group of Aborigines and other young people. Benedict will then tour through Sydney in a parade that is expected to shut down most of the downtown district. He will join a crowd expected at a vigil before leading Mass next Sunday at the culmination of the festival.

Fisher said at least 100,000 pilgrims were already in Sydney with more arriving all the time, with thousands being billeted in churches and schoolhouses across the city. Impromptu song sessions and other celebrations broke out in parks and other public places in the city, where banners have been unfurled and scores of smaller gatherings organized.