WASHINGTON (Agencies) - Tens of thousands of faithful crammed into a baseball stadium here Thursday to give a joyful welcome to Pope Benedict XVI as he appealed for a new spirit of evangelism in America. The pontiff, on his first papal visit to the United States, was met by a huge roar from about 48,000 people as he rolled into the new Washington Nationals ballpark on a brilliant spring morning in his "pope-mobile." The usual che-ers of the base-ball fans were replaced by a deafening wall of sound from the crowds who had flocked into the stadium from dawn, turning it into a cathedral for a day. Four choirs led by tenor Placido Domingo then began singing a Hallelujah chorus in unison, as the pope reentered the stadium on foot and proceeded to the altar. The faithful heard Benedict appeal for a new spirit of evangelism to respond to America's "increasingly secular and materialistic culture." But the mood turned sombre as Benedict urged US Catholics to renew their faith and condemned the "tragic" sexual abuse of children by priests which has rocked the Church here. "No words of mine could describe the pain and harm inflicted by such abuse," he said. The Pope acknowledged that the US paedophile priests scandal caused "indescribable pain and harm" to victims but asked Catholics to love their pastors. The Church was making amends though, Benedict insisted, in dealing "honestly and fairly with this tragic situation and to ensure that children ... can grow up in a safe environment." In his homily, Benedict said Catholics in the US and around the world had to reinforce their own faith and seek new converts in responding to "signs of alienation, anger and polarisation" in society at large. "The challenges confronting us require a comprehensive and sound instru-ction in the truths of the faith," he said, decrying rising violence, looser morals, "and a growing  forget-fulness of God."The pop-e's message of universal faith was underlined by the presence at the service of a Sikh man wearing a tur-ban, who sat in front of a group of Jewish men wearing skull-caps. Opening the celebration, Washington Archbishop Donald Wuerl reflected on America's rich racial and religious diversity. "All of us at the Mass reflect the breadth of this family," he said. Top US Catholic clerics, seminary students, and ordinary Americans from around the country joined families with children in tow to hear the German-born pontiff. Crowds mobbed the stadium's conce-ssion stands, especially those selling official souvenirs marking Benedict's visit. Colonel Gary Studniewski, a US Army chaplain, said he came to the Mass to pray for the "stretched" men and women of the armed forces fighting in Iraq, Afghanistan and elsewhere. "They can't be here. They're in harm's way but I can be here to pray for them. No one wants peace more than military personnel who see the horrors of war and the difficulties of so many people around the world," he said.