US President Barack Obama visited Ground Zero to lay a wreath at a memorial to the nearly 3,000 victims of the 9/11 attack, days after US Navy Seals killed Al Qaeda chief Osama bin Laden in Pakistan, CNN reported.
Osama was considered the mastermind behind the attack on the World Trade Center.
Obama, in his first visit as president to the area, met and spoke privately with family members of the victims, firefighters and other rescue workers who died in the 2001 attack.
The president wants to meet with them and share with them this important and significant moment, a bittersweet moment, White House press secretary Jay Carney said.
Obama visited a firehouse and a police station before arriving at the memorial site for the wreath laying ceremony. Fifteen firefighters from the station on Manhattan's West Side, which houses Engine Company 54, Ladder Company 4 and Battalion 9, were killed Sep 11, 2001, more than from any other station.
Obama invited former president George W. Bush to join him, but Bush declined.
A spokesman for the former president said he appreciated the invitation but wished to stick to his policy of staying out of the public spotlight since leaving office.
For Bush, Ground Zero was the site of one of the iconic moments of his presidency.
Days after the World Trade Center towers collapsed, Bush travelled to the smouldering wreckage to thank the rescue workers, delivering a speech through a firefighter's horn.
The White House said it took no offence at Bush's decision not to attend, saying that Bush was invited in the spirit of unity that Obama said he hoped would prevail in the wake of Osama's killing, just as it prevailed after the killings perpetrated by bin Laden nearly a decade ago.
"We've made clear that this is a moment of unity for Americans and a moment to recall the unity that existed in this country in the wake of the attacks on 9/11," Carney said.
Obama had visited Ground Zero as a presidential candidate, but he had not been there since entering the White House.