Pope Benedict XVI arrived in Washington on Tuesday, his first visit to the United States as pontiff at a challenging time for the Roman Catholic Church in the country.

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Pope Benedict XVI in Rome on Tuesday prepares to board a plane bound for Washington. ((Plinio Lepri/Associated Press))

The Pope's Alitalia aircraft touched down at Andrews Air Force Base shortly before 4 p.m. ET, displaying both the U.S. and Vatican flags from its cockpit as it taxied.

Pope Benedict emerged from the aircraft smiling and waving to an enthusiastic crowd of students, church officials and worshippers who gathered to greet him in his only public appearance Tuesday.

President George W. Bush, first lady Laura Bush and their daughter, Jenna, welcomed the Pope on the tarmac in an unprecedented greeting ceremony complete with military honour guards and two brass bands.

It is the first time any U.S. president has greeted a leader or dignitary of any kind at the base. Neither Bush nor the Pope spoke with reporters.

While the Catholic church is considered strong, the Pope will face the challenge of restoring unity and faith in the wake of sex abuse scandals that have devastated the church and forced the payout of nearly $2 billion in settlements. 

Aboard the flight to Washington from Rome, Pope Benedict told reporters he was "deeply ashamed" about the sex abuse scandal, adding the church "will do whatever is possible that this does not happen in the future."

"We will absolutely exclude pedophiles from the sacred ministry," he told reporters.

In 2004, the bishops released a statistical review that found 4,392 priests had been accused of molesting children in 10,667 cases between 1950 and 2002.

During his six-day stay in the U.S., the Pope will travel to just two cities — Washington and New York.

About 12,000 people are expected to gather for his official visit to the White House on Wednesday, the same day the Pope will celebrate his 81st birthday.

But he will skip a gala dinner planned for the evening, instead attending a prayer service with American bishops. He will also celebrate mass at Washington's baseball stadium, Nationals Park.

While in New York, he will stop for prayer at Ground Zero, deliver a major address at the United Nations and celebrate mass at Yankee Stadium.

Meeting with victims uncertain

It is still unclear whether Pope Benedict will meet with any of the victims of the sex abuse scandal.

"It's a formidable challenge but he's a formidable man," said U.S. military Archbishop Timothy Broglio.

"We're obviously much more aware of the nature of this problem, of how the church has to respond to it and we're certainly much more attentive to it than we were before."

Cardinal Tarcisio Bertone, the Vatican secretary of state, told the Associated Press in an interview last week that Pope Benedict will seek healing and reconciliation as he addresses a gathering of clergy at New York's St. Patrick's Cathedral.  

John Allen, who writes for the National Catholic Reporter, said he believes the Pope will offer "an expression of deep regret" for what has happened.

He added that the Pope also has a soft spot for America.

"People who are expecting him to come in and go negative in one form or another I suspect are going to be disappointed," Allen said.

"I suspect the dominant note will be a deep appreciation for the religious vitality of American society," he said.

With files from the Associated Press