America has marked the third anniversary of the 11 September terrorist attacks.
In New York, a ceremony at Ground Zero featured parents and grandparents who read the names of the 2,749 victims of the World Trade Center attacks.
Dignitaries, emergency workers and community leaders were also present.
The moment of impact of both hijacked airliners and the fall of each of the Twin Towers were marked by silences.
Later in the evening, powerful spotlights will send two shafts of light up into the night sky to symbolise the fallen structures.
A wreath was laid at the Pentagon and bells were rung in Pennsylvania to mark the other two attacks.
In Washington, President Bush vowed an unrelenting hunt against terrorists around the world.
In an address to the nation marking 11 September, Mr Bush said the United States was determined to stay on the offensive.
Nineteen al-Qaeda Islamist militants hijacked four US domestic airliners on 11 September 2001. They flew two into the Twin Towers of the World Trade Center, one into the Pentagon and the fourth crashed short of its target.
In a separate development, the owner of the World Trade Center site is suing the Saudi Arabian government for damages it suffered in the attacks.
The lawsuit has been filed by the Port Authority of New York and New Jersey.
