The president made the unprecedented gesture of greeting the Pope's plane
Pope Benedict XVI has received an unprecedented presidential greeting from George W Bush after arriving for his first official visit to the US.
Mr Bush and his wife Laura were waiting on the tarmac at Andrews Air Force Base when the Pontiff's plane touched down.
During his six-day visit, the head of the Catholic Church will address the UN and lead prayers at Ground Zero.
Before arriving the Pope told reporters on board his plane that he was "deeply ashamed" of sexual abuse by US clergy.
Pope Benedict, who was elected three years ago, vowed to work against a recurrence of the crisis, which tarnished the Church's reputation, saying "we will absolutely exclude paedophiles from the sacred ministry".
In recent years, the US Catholic Church, which has around 65 million followers, has paid $2bn (£1bn) to settle clergy sexual abuse cases.
The BBC's David Willey, who is travelling with the Pope, says that damage limitation over past scandals is not the main purpose of the Pontiff's first trip to the US though.
Our correspondent says he wants to deliver a message of Christian hope to American Catholics and non-Catholics alike, describing his journey as a pilgrimage to a "great people and a great country".
Hundreds of spectators had turned out for Pope Benedict's arrival at Andrews Air Force Base, near Washington.
The crowds cheered and clapped as he made his way onto the runway to be met by Mr Bush, his wife Laura and daughter Jenna.
On Wednesday, the Pope will pay a formal call upon Mr Bush at the White House.
It is more important to have good priests than many priests
During the flight from Italy, he said he would talk to Mr Bush about the plight of some Hispanic immigrants in the US, our correspondent says.
The US Church has been changing in recent years with the arrival of millions of new Latino immigrants.
The Pope also paid tribute to the fact that there was no state religion in the US, adding that a secular state where all religions can be welcomed is a positive model from which Europe can learn, our correspondent adds.
During the visit the Pope is due to celebrate two huge Masses at baseball stadiums in Washington and New York, as well as praying at Ground Zero, the New York site where the World Trade Centre was destroyed on 11 September 2001.
Although there have been 24 previous meetings between a sitting US president and a Pope - and Benedict XVI's predecessor, John Paul II, visited the White House in 1979 - there will be numerous firsts during this visit.
The Pope spoke about the church sex abuse scandals in the US
A crowd expected to number 10,000 will gather on the White House's South Lawn on Wednesday to mark his official arrival.
The unprecedented crowd, even larger than the 7,000 who greeted Queen Elizabeth II during a 2007 visit, will hear the anthems of both the US and the Holy See, as well as a 21-gun salute.
Mr Bush is due to host a lavish dinner in the White House's East Room to mark Pope Benedict's 81st birthday on Wednesday.
The meal's Bavarian-style menu will celebrate the Pope's German heritage, although the Pontiff himself is unable to attend.
Instead, he is expected to lead US bishops in a prayer service in Washington.
The BBC's Jonathan Beale in Washington says the theologically conservative Pope may get a warmer reception for his views in the US than in Europe.
Mr Bush is close to the Pontiff in opposing abortion, gay marriage and stem cell research.
But the two differ on issues including the war in Iraq and capital punishment, both of which the Vatican has opposed.
On board his flight to Washington, the Pope briefed reporters on his handling of the clerical sex-abuse crisis.
The sexual abuse by clergy had been a great suffering for the US Catholic Church and for him personally, he said.
"I am deeply ashamed and will do whatever is possible so that this does not happen in the future," he said.
"It is more important to have good priests than many priests. We will do everything possible to heal this wound."
The Pope has been asked to meet some victims of clerical abuse and their families during his visit but has so far declined to do so.
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