US President Barack Obama and his Republican challenger for the White House, Mitt Romney, have given Americans a day off from negative advertising and cutting politics on the 11th anniversary of the September 11 terrorist attacks.
With the November 6 election less than two months away, however, neither candidate was staying out of sight. Mr Obama observed a moment of silence at the White House before visiting the Pentagon, the target of one of four planes al Qaida hijacked 11 years ago
Mr Obama laid a white floral wreath at the US defence headquarters, and a moment of silence began at precisely 9.37am, when the Pentagon was hit. Mr Obama stood with his arms folded and head bowed as a bugler played, then raised his hand to his heart.
In remarks recalling the horror and lingering sorrow of the attacks, he declared: "Our country is safer and our people are resilient."
At the time of the White House ceremony, Mr Romney was shaking hands with firefighters at Chicago's O'Hare Airport, their yellow trucks forming a backdrop that recalled the sacrifice of first responders to the attacks.
The Republican nominee was flying to Nevada to address the National Guard, whose members deployed as part of the military response.
"On this most sombre day, those who would attack us should know that we are united, one nation under God, in our determination to stop them and to stand tall for peace and freedom at home and across the world," Mr Romney said in a written statement.
Vice president Joe Biden marked the day at a memorial service at Shanksville, Pennsylvania, where one of the hijacked airliners crashed after passengers fought the terrorists. Mr Biden grew up in nearby Scranton.
In a dramatic turn-around from the two previous presidential elections after the 2001 attacks, the race this year has been dominated by the economy rather than national security concerns.
Polls show Mr Obama leading Mr Romney on terrorism and national security issues, but both are a low priority for voters concerned about sluggish economic growth and an unemployment rate still above 8%. A CBS News/New York Times poll conducted in July found just 37% of voters called terrorism and security extremely important to their vote, while 54% said the economy and jobs were uppermost.