Bush Leads First 9/11 Anniversary Ceremony
George W Bush has led the first of the 9/11 commemorations as America prepares to mark the 10th anniversary of the day that changed the world.
Video: Mr Bush speaking in Shanksville, Pennsylvania
The former US president, joined by his wife Laura, laid a wreath of white flowers at the Pentagon in silent remembrance.
He placed it by the 9/11 memorial stone embedded in the wall outside Corridor 4 - near where hijacked American Airlines Flight 77 crashed into the building, killing 184 people.
Mr and Mrs Bush are now in Shanksville, Pennsylvania, for the dedication of the United Flight 93 memorial.
Forty passengers and crew died on board the aircraft, which plummeted to the ground during an onboard struggle to thwart hijackers who had seized the plane.
Earlier, President Barack Obama and the First Lady paid an emotional visit to Arlington Cemetery in Virginia, where they spent time among the graves of US servicemen and women killed in Iraq and Afghanistan.
Mr Obama, who will take part in various ceremonies tomorrow, also called for national unity and reflected on a decade that tested America's character.
"The terrorists who attacked us that September morning are no match for the character of our people, the resilience of our nation or the endurance of our values," the President said in his weekly radio and internet address.
"We're doing everything in our power to protect our people. And no matter what comes our way, as a resilient nation, we will carry on."
Mr Obama sought a balance between remembering and moving forward. He also tried to summon the feeling of unity that existed after terrorists killed nearly 3,000 people.
"They wanted to deprive us of the unity that defines us as a people. But we will not succumb to division or suspicion.
"We are Americans, and we are stronger and safer when we stay true to the values, freedoms and diversity that make us unique among nations."
Mr Obama thanked American troops who have served in the post-September 11 wars in Iraq and Afghanistan.
He praised the military successes that led to advances against al Qaeda and the killing of the group's leader, Osama bin Laden.
He also reaffirmed his commitment to winding down the conflicts he inherited.
"Yes, we face a determined foe, and make no mistake they will keep trying to hit us again.
"But as we are showing again this weekend, we remain vigilant. We're doing everything in our power to protect our people."
Meanwhile, intelligence officials have been working around the clock to determine the validity of a new threat of a possible al Qaeda attack on New York or Washington timed to coincide with the anniversary.
Mr Obama, who was a state senator in Illinois at the time of the attacks, is scheduled to visit New York City, Shanksville, Pennsylvania, and the Pentagon tomorrow.
In the evening, he plans to speak at a memorial event at the Kennedy Centre in Washington.