White House marks September 11th with memorial service
11 September 2013 Last updated at 14:30 BST
The White House has marked the 12th anniversary of the 11 September 2001 attacks with a memorial service.
The Brooklyn Youth Chorus performed the National Anthem before the President Obama and his wife Michelle, together with Vice-President Joe Biden and his wife Jill, marked the first minute of silence in observance of the time the first plane struck the North Tower.
Further silences were observed to mark the exact moment of each attack.