LONDON - Police raided a garbage depot and arrested street cleaners in a suspected terror plot against Pope Benedict XVI on Friday. Undeterred, the pontiff stuck to his message, reaching across Britain's religious and secular divide to demand a greater role for faith in public life.

Despite the six arrests, the pope did not alter a schedule rich in symbolism in this officially Protestant country with a history of anti-Catholicism: He prayed with the Archbishop of Canterbury and became the first pope to worship in Westminster Abbey.

Benedict also addressed political, cultural and business leaders in Westminster Hall, for centuries the center of British political life, asserting "the legitimate role of religion in the public square."

Among those in attendance were Tony Blair - a prominent convert to Catholicism - as well as former prime ministers Margaret Thatcher, John Major and Gordon Brown.

Faith, the pope said, "is not a problem for legislators to solve, but a vital contributor to the national conversation."

Benedict was informed of the pre-dawn arrests while visiting a Catholic college, the first stop on the busy second day of his state visit.

Five of the suspects were street cleaners arrested at a garbage depot in central London and a sixth was picked up later in the day. All six were arrested "on suspicion of the commission, preparation or instigation of acts of terrorism." Police said they ranged in age from 26 to 50, and media reports said some were Algerian, though authorities would not confirm that.

Police said they received information about a potential threat against the pope overnight, prompting the arrests under Britain's Terrorism Act. All six were being questioned and had not been formally charged.

At the scene of the street cleaners' arrests in Chiltern Street, near the famed Madame Tussauds wax museum, police cordoned off part of the road. Police officers, some dressed in white protective overalls, removed items from the depot, and examined garbage cans.

The street cleaners worked for a contractor on behalf of Westminster Council, the authority responsible for much of central London, including the Houses of Parliament, Westminster Abbey and other sites on the pope's itinerary Friday. However, the arrests took place at a depot responsible for cleaning another part of the city.

A street sweeper at the depot said at least one of those arrested was Algerian and he believed all five were from North Africa. He spoke on condition of anonymity because he was not authorized to talk to the media.

There have been no known plots against Benedict in his five-year papacy. His predecessor, Pope John Paul II, was gravely wounded in a 1981 assassination attempt.

Benedict's visit has been overshadowed by disgust over the Catholic Church's clerical abuse scandal and opposition from secularists and those who oppose the church's positions on homosexuality and using condoms to fight AIDS.

Security has been visibly higher than on Benedict's previous foreign trips, and Vatican officials have acknowledged that Britain represents a greater threat than other European countries the pope toured this year, including Portugal, Malta and Cyprus.

News of the arrests came as the pope was meeting representatives of other religions, including Muslims and Jews. He stressed the importance of mutual respect, tolerance and freedom to follow one's conscience.

The Vatican said Benedict was informed of the arrests and was pleased he could stick to his schedule.

"We have complete trust in the police," Vatican spokesman the Rev. Federico Lombardi told reporters. "The police are taking the necessary measures. The situation is not particularly dangerous."

"The pope is happy about this trip and is calm."

Hours after the arrests, Benedict met with the Archbishop of Canterbury Rowan Williams, spiritual leader of the worldwide Anglican Communion that grew from King Henry VIII's break with Rome in the 16th century.

The meeting came amid new tensions following Benedict's decision to initiate fast-track conversions to Catholicism for Anglicans who oppose the ordination of women as bishops.

Benedict and Williams greeted each other warmly, with the pope saying he had no intention of speaking of difficulties "that are well known to everyone here." Rather, he stressed the need for Christians to work together and bring a greater sense of virtue into public discourse.

Williams, who has not hidden his dismay over the Vatican's overture to conservative Anglicans, also stressed the need to bring the two churches together, saying each was "made less by the fact of our dividedness."

As he entered Westminster Abbey for an ecumenical service with Williams, the pope shook hands with a female Anglican priest. The ordination of women is one of the major issues dividing the churches.

Benedict's next stop was Westminster Hall, an ornate vaulted structure that carries potent symbolism as the site of the trial of Sir Thomas More, a Catholic who was beheaded for treason in 1535 because he refused to accept Henry VIII as head of the Church of England. More was canonized as a Catholic saint in 1935 and later added to the Anglican canon of saints.

In his address, Benedict praised Britain's democracy as a model worldwide, but lamented that religion, particularly Christianity, was increasingly marginalized from political decision-making.

"There are those who would advocate that the voice of religion be silenced, or at least relegated to the purely private sphere," the pontiff said. "There are those who argue that the public celebration of festivals such as Christmas should be discouraged, in the questionable belief that it might somehow offend those of other religions or none."

"These are worrying signs of a failure to appreciate not only the rights of believers to freedom of conscience and freedom of religion, but also the legitimate role of religion in the public square."

Benedict's day began with a noisy welcome from thousands of cheering Catholic schoolchildren at St. Mary's University College in London, where he urged them to ignore the shallow temptations of today's "celebrity culture."

Benedict also told their teachers to provide the children with a trusting, safe environment - the second time he has addressed the church sex abuse scandal during the visit. On Thursday, the pope acknowledged the church had failed to act quickly or decisively enough to remove pedophile priests from ministry.

"Our responsibility toward those entrusted to us for their Christian formation demands nothing less," Benedict said. "Indeed, the life of faith can only be effectively nurtured when the prevailing atmosphere is one of respectful and affectionate trust."

Polls in Britain indicate widespread dissatisfaction with the way Benedict has handled the sex abuse scandal, with Catholics nearly as critical of him as the rest of the population.

The pope gave a special greeting to 39-year-old Becky Gorrod and her 8-month-old daughter Alice. Mother and child were ushered in to meet the pontiff as the crowd cheered.

"My husband's never going to believe me," Gorrod said. "They opened the car door, and the pope got out. Then the (pacifier) fell out of Alice's mouth, and the pope bent down and picked it up! The pope! How mad is that?"

She said the pope then kissed Alice on the forehead.

A few blocks away, about 30 people protested, holding up inflated condoms and posters that read, "Condoms are not crimes."

One protester, 60-year-old Michael Clark, said he is gay and opposes the pope's visit because it is costing British taxpayers $18.7 million (12 million pounds) for security.

"That means it's being supported by taxpayers and people who may not have the same ideas," Clark said. "Sexuality is not evil."