By Philip Pullella and Tom Heneghan

NEW YORK (Reuters) - Pope Benedict ended his U.S trip on Sunday with an emotionally charged visit to Ground Zero where he prayed at the site of the felled World Trade Center, and a triumphant Mass for 57,000 people at Yankee Stadium.

His final day in the United States started with an eerie and somber visit to the symbol of the September 11 attacks by al Qaeda and ended with a religious service at the preeminent shrine of baseball, "the great American pastime."

At Ground Zero, now a gaping crater, he prayed for the victims, their families and an end to hate and violence.

In the most intense public portion of his first papal visit to the United States, Benedict blessed the area -- considered hallowed ground by many -- and comforted each of 24 special guests as a lone cellist played somber music.

They were 16 relatives of people killed when the jets hit the towers and eight survivors -- four World Trade Center workers and four first responders who rushed to help. Some were Catholics and kissed his ring as they told their story.

Fog shrouded tops of towering skyscrapers as the pontiff, 81, dressed in a long white wool coat against the chill wind and damp, read a prayer for those who died at Ground Zero, the Pentagon and on United Flight 93, which crashed in Pennsylvania after passengers overwhelmed the hijackers.

"God of peace ... turn to your way of love those whose hearts and minds are consumed with hatred," he said, after blessing the site with holy water and lighting a large candle symbolizing sacrifice and resurrection.

"Grant that those whose lives were spared may live so that the lives lost here may not have been lost in vain. Comfort and console us, strengthen us in hope, and give us the wisdom and courage to work tirelessly for a world where true peace and love reign among nations and in the hearts of all."

It was eerily silent at the construction site 75 feet (25 meters) below street level at the geological bedrock that supports Manhattan's skyscrapers. Some survivors cried.

One of those attending was John McLoughlin, a Port Authority of New York and New Jersey Police officer who was one of the last people pulled out and who was the focus of the Oliver Stone movie "World Trade Center" starring Nicolas Cage.

THIRD 'SERMON ON THE MOUND'

At the departure ceremony at Kennedy Airport, Benedict told Vice President Dick Cheney that Ground Zero would "remain firmly etched in my memory as I continue to pray for those who died and for all who suffer in consequence of the tragedy."

After a chilly start to the day in lower Manhattan, the sun came out in the afternoon in the Bronx when some 57,000 cheering people welcomed the pontiff to Yankee Stadium, known as "the House that Ruth built" after legendary 1920s slugger Babe Ruth.

There, he became the third pope to deliver what has come to be known as "the sermon on the mound," a term coined in 1965 when Pope Paul VI said Mass there because the papal altar is near the spot where the pitcher throws the ball.

The crowd got on their feet and gave him an ecstatic welcome as he entered and rode around in a bullet-proof "popemobile."

Saying Mass from a yellow, white and purple altar platform, Benedict said faith meant not being discouraged by difficulties, even when they enveloped the Church itself.

"It means not losing heart in the face of resistance, adversity and scandal," he said in his sermon, in an apparent reference to the sexual abuse scandal in the United States, a major theme of his trip.

The loudest applause came when the pope denounced abortion, calling for protection of the rights of "the most defenseless of human beings, the unborn child in the mother's womb."

He also rejected "a false dichotomy between faith and political life," a reference to the Church's position that Catholic politicians cannot support abortion or gay marriage in the name of pluralism or democracy.

At Ground Zero, the passage in his prayer about those with "minds consumed with hatred" has stirred controversy because some people interpreted it as a prayer for hijackers who were killed in the attacks and their backers.

Asked about the prayer, New York Mayor Michael Bloomberg said he had no concerns about the content.

"I think that he has always been a man of peace and a man who believes we should live together and he is praying for everyone," Bloomberg told Reuters at Ground Zero.

(Writing by Philip Pullella; editing by Todd Eastham)

(For more on religion, see the Reuters religion blog FaithWorld at http://blogs.reuters.com/faithworld)