US president George W Bush today embarked on nearly 24 hours of sombre observances at the three sites where 9/11 terrorists wrought death and destruction and transformed his presidency.

Millions of Americans will today commemorate the fourth anniversary of the September 11 terrorist attacks.

New York Mayor Rudolph Giuliani said goodbye today to the city where he battled crime, his critics and the September 11 crisis across eight years in City Hall.