9/11 Memorial Services: President Obama Lays Wreath at Pentagon as Nation Observes Moment of Silence

President Barack Obama has led the nation in marking the 12th anniversary of the September 11 terrorist attacks, addressing families of survivors at a private Pentagon ceremony in Washington, D.C. Obama laid a wreath in remembrance of the Americans who lost their lives that day, as thousands of Americans across the nation also gathered at 9/11 memorials to hold moments of silence and pay their respects to those who had passed.

(Photo: Reuters/Gary Cameron)U.S. President Barack Obama bows his head during a prayer at remembrance ceremonies for 9/11 victims at the Pentagon 9/11 Memorial in Washington September 11, 2013.

Obama spoke at the Pentagon shortly after a moment of silence was observed at 9:30 a.m. ET, the time 12 years ago when al-Qaeda terrorists flew an American Airlines jet into the Pentagon, killing a total of 184.

"It is an honor to be with you here again to remember the tragedy of 12 Septembers ago to honor the greatness of all who responded, and to stand with those who still grieve, and to provide them some measure of comfort once more," the president said to the families of the victims killed at the Pentagon.

"We pray for you and the families who have known the awful depths of loss. In the quiet moments we've spent together from the stories you've shared, I am amazed in the will that you've summoned in your lives to lift yourselves up and to carry on, to live and love and laugh again," Obama added. The Pentagon memorial service was also attended by Secretary of Defense Chuck Hagel and Chairman of the Joint Chiefs Gen. Martin E. Dempsey.

"Our hearts still ache for the futures snatched away," Obama added.

Before attending the Pentagon ceremony, Obama and Biden joined their wives outside the White House, on the south lawn, to observe a national moment of silence for the victims as a bell tolled, while the Justice Department also observed a moment of silence.

At the 9/11 memorial site in lower Manhattan, New York, over 1,000 people gathered for a moment of silence at 8:46 a.m. when American Airlines Flight 11 crashed into the North Tower of the World Trade Center, beginning the tragic day that resulted in the death of 2,977 people. Those in attendance at the New York City memorial observed a second moment of silence at 9:03 a.m., when the second plane, United Airlines Flight 175, crashed into the South Tower.

Bagpipes and bells played as more than a thousand people gathered at the Twin Towers' memorial for the annual reading of names of the deceased from both the 1993 and 2001 attacks on the World Trade Center. No public officials spoke at Wednesday's NYC ceremony, although major public leaders, including Mayor Bloomberg and former Mayor Giuliani, were in attendance.

Americans also gathered at the site in Shanksville, Pa. to hold a moment of silence at 9:45 p.m., where 40 people died when passengers on board United Airlines Flight 93 attempted to re-take control of the plane seized by al-Qaeda terrorists, ultimately crashing it into an empty field in the small rural town in southwestern Pennsylvania.

September 11th proved to be the deadliest attacks on American soil in the nation's history. Several cities across the U.S. will hold memorial services today to honor those who passed in the tragic terrorist attacks 12 years ago, including the First Responder firefighters and policemen who died in their heroic attempts to rescue civilians.