Despite the momentous nature of the Al-Qaeda leader's death, almost a decade after the attacks drove a wedge between the West and the Muslim world, the ceremony was low-key and somber: a remembrance of those fallen rather than a victory celebration.
Obama, making his first visit to Ground Zero as president, did not make a speech, but solemnly bowed his head and observed a moment of silence after laying the wreath along with city officials.
He did speak briefly earlier at a firehouse that lost 15 men battling the infernos on 9/11, issuing a stark message to America's enemies around the world. "When we say we will never forget, we mean what we say," he said.
Obama is to visit Fort Campbell in Kentucky on Friday to meet some of the elite commandos who sneaked into Pakistan in stealth helicopters and took out bin Laden in the death of night.
The president "will have the opportunity to privately thank some of the special operators involved in the operation," a US official said on condition of anonymity.
The commandos who swooped on Osama bin Laden's compound in Abbottabad on Monday reportedly came from a renowned squad known as "Team Six," an elite unit drawn from the already elite ranks of the SEALs.
The fallout from the covert pre-dawn raid meanwhile intensified with Pakistan's military demanding the United States cut its troop presence in the country to a "minimum."
After days of questions in Washington over how bin Laden could have found shelter under military noses, Pakistan's army chief of staff General Ashfaq Kayani threatened to "review" cooperation in the event of another US raid.
A key US ally in the war against Islamist militants in Afghanistan, Pakistan has admitted "shortcomings" in developing intelligence on bin Laden's whereabouts and ordered an investigation.
But Islamabad is fighting hard to allay suspicions that bin Laden could have had some kind of support from its military intelligence services.
"It's easy to say that the Inter-Services Intelligence (ISI) or elements within the government were in cahoots with the Al-Qaeda," top foreign ministry official Salman Bashir said.
"This is a false hypothesis. This is a false charge. It cannot be validated on any account and it flies in the face of what Pakistanis and in particular the Inter-Services Intelligence has been able to accomplish."
In Washington and beyond there is incredulity that bin Laden could have found shelter for up to six years in Abbottabad, a leafy garrison town just two hours' drive from the capital.
In a sign of complete US distrust of its key ally, CIA chief Leon Panetta said Washington kept Islamabad in the dark about the raid for fear of the Al-Qaeda chief being tipped off.
Despite some US lawmakers questioning billions of dollars in US assistance and accusing Pakistan of playing a double-game, key leaders in Congress voiced support Thursday for preserving aid.
"It's not a time to back away from Pakistan: It's time for more engagement with them, not less," House Speaker John Boehner told reporters.
The United States has given some $18 billion to Pakistan since the September 11, 2001 attacks, when the nuclear-armed nation officially ended support of Afghanistan's Taliban and agreed to work with the United States.
While quietly rejoicing at the elimination of America's most wanted man, the Obama administration has been forced to defend the legality of the raid, after acknowledging that bin Laden was unarmed when he was shot fatally above the left eye.
The administration's account of the raid has shifted, with officials providing new details to US media that described a one-sided clash instead of the raging firefight initially claimed.
Officials said the commandos encountered only one man who was armed -- bin Laden's courier -- who fired the only shots near the outset of the operation.
The team of about two dozen SEALs shot and killed the courier and a woman in the guesthouse and were not fired on again, officials told US media.
In a separate main building the courier's brother and another man, thought to be bin Laden's son Khalid, were shot dead on the first floor. The courier's brother was believed to be about to fire a weapon.
Bin Laden was shot in the chest and head in his bedroom on the third floor, where the commandos found an AK-47 rifle and a Russian pistol. His Yemeni wife was shot and injured in unclear circumstances.
The assault force, who brought along a specially trained dog, also reportedly found a false door, obstacles on the stairs in Bin Laden's residence and a number of other weapons.
The latest account differed from the White House version of events offered on Tuesday, when a spokesman said the US troops "were engaged in a firefight throughout the operation."
Obama on Wednesday opted against releasing photos of bin Laden's corpse, citing national security risks and saying the United States should not brandish "trophies" of its victory.
Bin Laden's body was buried at sea off a US warship to prevent any grave on land from becoming a shrine. The Abbottabad compound that served as his lair has instead become a macabre monument to the Al-Qaeda leader.
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