A day before the anniversary commemorations, the president made a pilgrimage to Arlington National Cemetery, strolling with his wife, Michelle, among graves filled with dead from the Afghanistan and Iraq wars.
And he invoked the common purpose that arose from carnage a decade ago in telling Americans that the nation cannot be broken by terrorism "no matter what comes our way."
Obama also visited a soup kitchen, where he and his family helped prepare trays of gumbo for the needy in the nation's capital, underscoring the call to national service that rang so loudly after the terrorist attacks.
All this as the president and his national security team tracked the latest possible terrorist threat against the country, a tip that al-Qaida might be seeking to detonate a car bomb in New York or Washington.
Obama met his senior national security team in the morning to review the latest developments and ensure the nation remains on a heightened state of vigilance during the anniversary commemorations.
As of Saturday U.S. intelligence agencies had not found evidence that al-Qaida had sneaked any terrorists into the country to carry out an anniversary attack.
At D.C. Central Kitchen, Obama said projects to serve the community "are part of what the spirit of remembering 9/11's all about - the country being unified and looking out for one another."
In an email to supporters, the president urged others to follow his lead. "With just a small act of service, or a simple act of kindness towards others, you can both honor those we lost and those who serve us still, and help us recapture the spirit of generosity and compassion that followed 9/11," the president wrote.
Earlier, at Arlington, he and his wife held hands with each other and hugged other visitors among rows of white tombstones from the long wars that Obama is winding down after more than 6,000 American troop deaths.
"It's a reminder that our way of life is dependent on the incredible courage, the incredible patriotism of a whole host of people from all across the country, every walk of life, every ethnicity, every religion," the president said in an interview with NBC Nightly News broadcast later Saturday. "It's a somber moment when you think about all these young people who gave their lives so young."
Obama, a little-known state senator in Illinois at the time of the attacks, now has the responsibility to help lead the nation in remembrance of a trauma 10 years on.
On Sunday, the president is scheduled to visit all three sites where hijacked planes struck - New York City, Shanksville, Pa., and the Pentagon - before delivering evening remarks at a memorial event at the Kennedy Center in Washington.
In his weekly radio and Internet address Saturday, Obama sought a balance between remembering the attacks and the nearly 3,000 people who died, and moving forward.
He thanked troops who have served in the post-Sept. 11 wars in Iraq and Afghanistan, and praised the military successes that led to advances against al-Qaida and the killing of the group's leader, Osama bin Laden.
"A decade after 9/11, it's clear for all the world to see - 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.
"They wanted to terrorize us, but, as Americans, we refuse to live in fear. 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. And no matter what comes our way, as a resilient nation, we will carry on."
Former New York City Mayor Rudy Giuliani, who gave the weekly Republican address, said the terrorists achieved their goal of killing Americans, but failed to destroy the American spirit.
"The country was not broken, but rather, it was more united in the days after Sept. 11 than at any time in my lifetime," Giuliani said.
Without mentioning Obama by name, Giuliani also used his address to criticize the administration's policies, saying that America is safer, but not as safe as it should be. "Perhaps the most dangerous impulse we've developed since Sept. 11 is impatience demonstrated by the calls to put our armed forces on timetables," Giuliani said.