Americans are marking the fifth anniversary of the September 11th terrorist attacks on Monday, by observing moments of silence and reading the names of the victims.
President Bush visited all three sites scarred by the attacks that killed nearly three thousand people within a few hours, making them the deadliest ever on American soil.
Mr. Bush and his wife Laura laid a wreath at the Pentagon, where one of the four hijacked airplanes crashed, killing 184 people.
Earlier, he took part in a memorial service in a field (near Shanksville) in Pennsylvania, where a hijacked jet crashed after passengers tried to overpower their captors. The airliner carrying 40 people and four hijackers is believed to have been headed to the White House or the U.S. Capitol.
President Bush also joined firefighters and police officers at a firehouse in New York City. They bowed their heads and paused in silence twice -- at the exact times hijackers rammed two airliners into the World Trade Center, destroying the famous twin towers.
Bagpipes played at Ground Zero, the barren pit where the Twin Towers once stood. Spouses and partners of the 2,749 people killed in the towers read aloud the victims' names, one at a time. Other family members gathered to listen, many holding photographs of their loved ones and leaving behind bouquets of flowers.
Memorial observances for the September 11th victims were also being held across the United States and in other countries, including Russia and Britain.
The president will address the nation from the White House Monday evening (just after 1 hour, Universal Time, Tuesday).
At the Pentagon, Vice President Dick Cheney said that September 11th has ceased to be an ordinary day on the calendar. He said after the attacks, grief soon hardened into resolve.