SHANKSVILLE, Pa. - On a day of serenity and remembrance, President Barack Obama honored the dead of Sept. 11 with his quiet presence Sunday at the three most tangible reminders of both the incredible loss and dauntless resilience of a country rebuilding a decade later.

At New York's ground zero, Obama touched the names of the lost etched into bronze at a memorial pool created in the footprint of one of the downed World Trade Center towers.

In a field in rural Pennsylvania, he walked the marbled Wall of Names and placed a wreath memorializing the 40 people who crashed at Shanksville after fighting back against the hijackers and driving their plane into the ground.

At the Pentagon, too, the president placed a wreath at a memorial where each of 184 victims is remembered with a bench and small reflecting pool. A military band played a soulful rendition of "Amazing Grace" as the president greeted visitors to the memorial.

This was not a day centered on presidential speechmaking. Rather, Obama's principal role was simply to be there as the nation paused to remember the nearly 3,000 lives lost and ponder all that has transpired.

At a ceremony at ground zero, Obama read Psalm 46, which he chose because it speaks of perseverance through challenges.

"God is our refuge and strength," Obama intoned, "a very present help in trouble. Therefore, we will not fear."

On a sun-splashed New York morning, Obama and his wife, Michelle, first walked with former President George W. Bush and his wife, Laura, to the North Memorial Pool. All four touched the names etched in bronze and silently bowed their heads. They then turned to dispense greetings and hugs to family members of those who died.

This also was not a day for partisanship or rancor.

Bush gave Obama a quick nod of solidarity after the president's reading. It was the first time the two presidents had seen each other since their Rose Garden appearance after the Haiti earthquake in January 2010.

The presidents and their wives stood behind bulletproof glass during the ceremony, an indication of the tight security surrounding the day's events. In Washington, Obama's chief counterterrorism adviser convened a meeting in the Situation Room to review security precautions for the weekend.

Obama's stop in Shanksville drew spontaneous applause and chants of "USA" from those at the memorial site, where each of the 40 marble slabs is inscribed with the name of someone who died in the crash. Obama and his wife lingered at the site to pose for photos with visitors, greet children and share some quiet laughs.

"Thanks for getting bin Laden," one man called out.

The Obamas then walked to the boulder that marks the actual crash site and stood quietly together in a field of wildflowers for a time.

"I think it's just important that the president shows his support for the families that lost loved ones," said Jaleel Dyson, an 18-year-old from Washington who attends college in the area and came to pay tribute to the dead.

Obama, who was a state senator from Illinois when the hijackers struck in 2001, has called on Americans this weekend to remember and serve, and to come together toward a joint future.

"Ten years later, I'd say America came through this thing in a way that was consistent with our character," he told NBC News. "We've made mistakes. Some things haven't happened as quickly as they needed to. But overall, we took the fight to al-Qaida, we preserved our values, we preserved our character."

Obama's only other planned public remarks Sunday were to come at a memorial concert in Washington in the evening.

His goals were to acknowledge how the country has changed, such as an increased vigilance against terrorism, and the things that have stayed the same, the values of freedom and liberty that bind the country together.

In the broadcast interview, Obama recalled going home after the attacks and rocking his baby daughter, Sasha. "Our first reaction was, and continues to be, just heartbreak for the families involved. The other thing that we all remember is how America came together."