President Obama at ground zero

President Barack Obama embraces unidentified family members of victims of the World Trade Center attack after laying a wreath at the National Sept. 11 Memorial at ground zero in New York, May 5, 2011.

Special report: The killing of Osama bin Laden

President Barack Obama greets the family of Glen James Wall, who died at the World Trade Center attack, after laying a wreath at the National Sept. 11 Memorial at ground zero in New York, May 5, 2011.

Special report: The killing of Osama bin Laden

President Barack Obama shakes hands with a New York Police Department officer after a wreath laying ceremony at the National Sept. 11 Memorial at ground zero in New York, May 5, 2011.

Special report: The killing of Osama bin Laden

President Barack Obama observes a moment of silence during a wreath laying ceremony at the National Sept. 11 Memorial at ground zero in New York, May 5, 2011.

Special report: The killing of Osama bin Laden

President Barack Obama observes a moment of silence during a wreath laying ceremony at the National Sept. 11 Memorial at ground zero in New York, May 5, 2011.

Special report: The killing of Osama bin Laden

President Barack Obama lays a wreath at the National Sept. 11 Memorial at ground zero in New York, May 5, 2011.

Special report: The killing of Osama bin Laden

President Barack Obama and a New York City Fire Dept. Lieutenant carry a wreath to be placed at the World Trade Center site, in New York, May 5, 2011.

Special report: The killing of Osama bin Laden

President Barack Obama prepares to lay a wreath at the National Sept. 11 Memorial at ground zero in New York, May 5, 2011.

Special report: The killing of Osama bin Laden

President Barack Obama walks with, from left, New Jersey Gov. Chris Christie, New York Gov. Andrew Cuomo, New York Mayor Michael Bloomberg, Port Authority Chairman David Samson, as they arrive for a wreath laying ceremony at the National Sept. 11 Memorial at ground zero in New York, May 5, 2011.

Special report: The killing of Osama bin Laden

President Barack Obama arrives with staff at the National Sept. 11 Memorial at ground zero in New York, May 5, 2011.

Special report: The killing of Osama bin Laden

President Barack Obama meets with police officers and first responders at the First Precinct before visiting the National Sept. 11 Memorial at ground zero in New York, May 5, 2011.

Special report: The killing of Osama bin Laden

President Barack Obama, accompanied by Police Commissioner Raymond Kelly, and others, meets with police officers and first responders at the First Precinct before visiting the National Sept. 11 Memorial at ground zero in New York, May 5, 2011.

Special report: The killing of Osama bin Laden

President Barack Obama speaks to firefighters and first responders at Engine 54, Ladder 4, Battalion 9, before visiting the National Sept. 11 Memorial at ground zero in New York, May 5, 2011. The visit comes four days after US commandos killed al-Qaeda leader, Osama bin Laden, in Pakistan.

Special report: The killing of Osama bin Laden

President Barack Obama speaks to firefighters and first responders at Engine 54, Ladder 4, Battalion 9, before visiting the National Sept. 11 Memorial at ground zero in New York, May 5, 2011.

Special report: The killing of Osama bin Laden

President Barack Obama and former New York City Mayor Rudy Giuliani, right, meet with firefighters and first responders at Engine 54, Ladder 4, Battalion 9, before visiting the National Sept. 11 Memorial at ground zero in New York, May 5, 2011.

Special report: The killing of Osama bin Laden

President Barack Obama, followed by former New York City Mayor Rudy Giuliani, arrives to meet with firefighters and first responders at Engine 54, Ladder 4, Battalion 9, before visiting the National Sept. 11 Memorial at ground zero in New York, May 5, 2011.

Special report: The killing of Osama bin Laden

President Barack Obama shakes hand with people after arriving at John F. Kennedy International Airport in New York, May 5, 2011, en route to ground zero to meet with first responders and family members of victims of the Sept. 11, 2001 attacks. The visit comes just days after he announced Sunday that Osama bin Laden had been killed by U.S. forces.

Special report: The killing of Osama bin Laden

A view of construction at the World Trade Center site on May 5, 2011, in New York.

Special report: The killing of Osama bin Laden

A Coast Guard boat patrols near the landing zone as President Barack Obama arrives in New York, May 5, 2011, to participate in a wreath-laying ceremony at the National Sept. 11 Memorial at ground zero.

Special report: The killing of Osama bin Laden

President Barack Obama greets guests after arriving at John F. Kennedy International Airport in New York, May 5, 2011, en route to ground zero to meet with first responders and family members of victims of the Sept. 11, 2001 attacks.

Special report: The killing of Osama bin Laden

President Barack Obama steps off Air Force One at John F. Kennedy International Airport in New York, May 5, 2011, en route to ground zero and a meeting with first responders and family members of victims of the Sept. 11, 2001, attacks.

Special report: The killing of Osama bin Laden

President Barack Obama waves as he steps off Air Force One at John F. Kennedy International Airport in New York, May 5, 2011, en route to ground zero and a meeting with first responders and family members of victims of the Sept. 11, 2001, attacks.

Special report: The killing of Osama bin Laden