NEW YORK (AP) ― President Barack Obama solemnly honored victims of the Sept. 11, 2001, terror attacks and declared that the killing of Osama bin Laden was an American message to the world: “When we say we will never forget, we mean what we say.”

Standing at the gritty construction site of ground zero Thursday, where the World Trade Center towers fell and a memorial now rises, the president laid a wreath of red, white and blue flowers for the nearly 3,000 who died.

For Obama, the day was about the importance of being in New York in the aftermath of the successful raid to find and kill bin Laden, the al-Qaida leader blamed for the attacks. Obama addressed families who have watched and wondered for nearly a decade whether the government would track down its most infamous enemy.

On this special ground, Obama never mentioned bin Laden’s name.

Still, this was where the terrorist inflicted his greatest damage in 2001 when hijacked airliners were crashed into the World Trade Center. Nearly 200 other people died when a third airliner hit the Pentagon ― Vice President Joe Biden led a ceremony there Thursday, and Bush Defense Secretary Donald Rumsfeld attended ― and others were killed when yet a fourth plane crashed in Pennsylvania.

Enthusiastic, emotional New Yorkers waited on streets to see the president, but there were few displays like the more raucous exuberance of a few days earlier. There were happy faces, shouts of “USA! USA!” and flags waved in the crowd, but there also was heavy security and most people were cordoned off blocks from where the president could be seen.

Bin Laden was shot dead in a raid on his Pakistan compound early Monday, the result of years of painstaking intelligence work and a covert military mission in which none of the U.S. commandos was killed.

Days after the 2001 attacks, President George W. Bush stood here with firefighters and a bullhorn. There was a different feel a decade later as another president paid his respects. Obama met with firefighters, then police, before having a solemn moment at ground zero and meeting privately with families of those who died.

“This is a symbolic site of the extraordinary sacrifice that was made on that terrible day,” the president said at Engine 54, Ladder 4, Battalion 9. The firehouse in New York’s theater district lost 15 firefighters on 9/11. The fire crews gave him hearty applause.

Obama said the American pursuit of the terrorist leader “sent a message around the world but also sent a message here back home that when we say we will never forget, we mean what we say, that our commitment to making sure that justice is done is something that transcended politics, transcended party.”

The president closed his eyes and clasped his hands at the outdoor memorial where the twin towers of the World Trade Center once dominated the Manhattan skyline.

Mammoth fountains and reflecting pools mark the “footprints” of the fallen towers. Now the nearby skyline is filled with construction machinery. The emerging skyscraper informally known as Freedom Tower is more than 60 stories tall.

It wasn’t a moment for celebrating the military operation that killed bin Laden; that may come Friday, when the president visits Fort Campbell, Kentucky, home to the Army unit involved in transporting Navy SEALS in and out of bin Laden’s compound. White House officials said Obama intended to privately thank participants in the raid.

Obama said Thursday he hoped the results of the raid on bin Laden’s compound showed that “we did what we said we were going to do, and that Americans, even in the midst of tragedy, will come together, across the years, across politics, across party, across administrations, to make sure that justice is done.”

Former New York Mayor Rudy Giuliani, who led the city in the days after the attacks, joined Obama during the day.

Obama invited Bush to join him Thursday in New York, but the former president declined.

Meanwhile, the debate over photos of bin Laden’s death continued. Obama announced earlier he does not intend to make them public.

Several Republican presidential hopefuls want them released.

Texas Rep. Ron Paul said Thursday that he sides with transparency when there is public doubt. Former Minnesota Gov. Tim Pawlenty said “it would have been OK to release the photos.” And former Alaska Gov. Sarah Palin accused Obama of “pussy-footing” on making the photos public.