In a letter to Archbishop Timothy Dolan of New York, the head of the U.S. bishops' conference, Benedict said he was praying for the thousands of innocent victims of the "brutal assault" and said he hoped that their families may find continued consolation.
He praised the "courage and generosity" that Americans showed in the rescue operations and in moving forward.
But the pope said the tragedy of the day was compounded by the attackers' claim to be acting in God's name. "Once again, it must be unequivocally stated that no circumstances can ever justify acts of terrorism," Benedict wrote.
He called for a greater commitment to justice and a "global culture of solidarity" to rid the world of the types of grievances that spark such acts of violence.
Both Benedict and Pope John Paul II before him voiced such themes frequently in the months and years following Sept. 11, 2001.