In New York, children guided thousands through a tearful September 11 remembrance, held under brilliant blue skies that were reminiscent of the day of the attacks in 2001.
A total of 200 children, mostly sons and daughters of the dead, read the names of the 2,792 killed at Ground Zero.
While the event was scaled down from the first anniversary, the three-hour ceremony still carried a powerful emotional punch, compounded by the new-found uncertainties of a country at war.
President George W Bush observed the first moment of silence on the South Lawn of the White House in Washington after attending a special church service.
“We remember lives lost. We remember the heroic deeds. We remember the compassion and the decency of our fellow citizens on that terrible day.”
Ceremonies were also held in Washington for the victims at the Defence Department headquarters where a third hijacked jet smashed into the building killing 184 people.
Meanwhile a bell tolled 40 times in a Pennsylvania field where a fourth jet crashed after an uprising by passengers against four al Qaeda hijackers, killing all 40 passengers and crew.
But nationals from 80 countries were killed in the attacks on New York and Washington, and mourning was held around the world.
World leaders also seized upon the anniversary to share the grief of the victims’ families and reaffirm their commitment to fight terrorism.
The danger of further attacks was emphasised by a US State Department warning that al-Qaeda could use the anniversary to stage a new strike “more devastating than the September 11 attack.”
The warning stated the European or Eurasian locations could be targeted “possibly to closely coincide with the anniversary of the September 11 attack”.