U.S. President Barack Obama embraces victims' family members as first lady Michelle Obama stands by at the 9/11 Memorial during the tenth anniversary ceremonies at the World Trade Center site in New York
U.S. President Barack Obama (2nd R) embraces victims' family members as first lady Michelle Obama (R) stands by at the 9/11 Memorial during the tenth anniversary ceremonies at the World Trade Center site in New York, September 11, 2011. The 9/11 attacks changed life in the United States forever, but 10 years after the devastating hit, New Yorkers have learned to live in a more dangerous world and are ready to move on. REUTERS

President Barack Obama picked up where his predecessor George W. Bush left off in the war against Islamic militants after the September 11 attacks, and on Sunday both saw the raw emotions that linger 10 years later.

The 10th anniversary of the attacks marked the first time the Democratic and Republican presidents have appeared together publicly since January 2010. But, joined by their wives, the two men made a show of solidarity at Ground Zero in New York, walking in tandem along a memorial pool at the site of the north tower of the World Trade Center.

They nodded their heads during a moment of silence, the only sound the roaring of the waterfall in the pool.

Afterward, they appeared together behind bullet-proof glass near where the names of those killed on September 11 were read aloud.

Obama read from Psalm 46, and Bush read an 1864 letter written by President Abraham Lincoln to a widow who had lost five sons in the Civil War that said the deaths were a sacrifice upon the altar of freedom.

Before speaking, Bush put on the podium a badge from New York Port Authority officer George Howard who died on September 11. Howard's mother gave Bush the badge when he visited Ground Zero three days after the attacks.

The crowd at Ground Zero was somber as survivors of the nearly 3,000 killed at the World Trade Center waved photos of lost loved ones.

MEMORIAL TO UNITED FLIGHT 93

At Shanksville, Pennsylvania, where Obama continued the commemoration, the mood was more upbeat. Obama and his wife Michelle were greeted with cheers and shouts of USA, USA in a grassy field where a memorial is being constructed for the passengers and crew of United 93.

You're my hero, someone yelled from the crowd as the Obamas shook hands and posed for pictures of families of the United 93 victims.

Afterward, the Obamas took a solemn stroll down a trail lined with wildflowers to a large boulder that marked the point of impact for the airliner, which was brought down after a passenger rebellion against the hijackers.

In one of the major successes of his presidency, Obama ordered the secret mission in May that led to the death of al Qaeda leader Osama bin Laden.

But neither the death of the man behind the September 11 hijackings nor the decade-old war in Afghanistan to dislodge the Taliban and defeat al Qaeda played a central role in Obama's day. Instead, it was filled with remembering those killed in the attacks, and looking ahead to renewal, a theme that was expected to emerge from his evening remarks at a Kennedy Center memorial event in Washington.

At the Pentagon, Obama placed a wreath of white flowers on a stand at the date line of the memorial outside the vast building, which says September 11, 2001 9:37 AM to mark the time the plane struck.

He then paused and bowed his head in a moment of silence before he and his wife went to greet and take pictures with victims' family members. The small crowd cheered when the Obamas first arrived, but the president maintained a serious expression for the somber wreath-laying ceremony. A military band played in the background.