Nearly 3,000 people were killed on September 11, 2001 when 19 Al-Qaeda suicide bombers hijacked four passenger jets, crashing them into the Twin Towers in New York, the Pentagon in Washington and a field in Shanksville, Pennsylvania.
It was the first foreign attack on the US mainland in almost two centuries and sparked US-led invasions of Afghanistan, in 2001, and Iraq, in 2003, where war rages on more than a decade later.
Countries in the Middle East from Libya to Syria are engulfed in war, providing a fertile ground for Al-Qaeda affiliates to breed, and Europe has been tormented by attacks inspired by the Islamic State group.
The names of the dead will be read out in a remembrance service at Ground Zero in New York on the site of the rebuilt World Trade Centre, and President Barack Obama will address a ceremony at the Pentagon.
“This weekend, we honour their memory once more. We stand with the survivors who still bear the scars of that day,” Mr Obama said on Saturday.
President Obama will observe a moment’s silence at the White House at 8:46 a.m. EDT before heading to the Pentagon where he will deliver an address during the memorial ceremony.
In his weekly radio and internet address Saturday, Obama lauded the bravery of survivors, of emergency personnel who rushed to help victims and all others who have worked on keeping the country safe since the attacks.
“In the face of terrorism, how we respond matters … We cannot give in to those who would divide us. We cannot react in ways that erode the fabric of our society. Americans will never give in to fear,” the president reportedly said. “We’re still the America of heroes who ran into harm’s way, of ordinary folks who took down the hijackers, of families who turned their pain into hope.”
The president also reiterated the country’s commitment in fighting against terrorist outfits like the al-Qaida and the Islamic State group. “We will destroy them. And we’ll keep doing everything in our power to protect our homeland,” he added.
“We’re going to be stronger, more resilient. That’s what this is about,” he said at the opening. “It took a lot of perseverance. It will also contribute to the economic vitality of the area.”
George W. Bush, who was U.S. president at the time of the attacks, will not attend the ceremonies in New York or Washington.
His office said he will go to church in Dallas, Texas, and then attend the Dallas Cowboys football home opener against the New York Giants. There he will participate in a ceremonial coin toss with two New York police officers who were present at Ground Zero on 9/11.