United States: Americans yesterday remembered the victims of September 11th, 2001, in solemn ceremonies at New York's World Trade Center, the Pentagon in Washington, and in a field at Shanksville, Pennsylvania, where United Flight 93 crashed.
President Bush started the fifth anniversary of the attacks with a group of firefighters in New York, and later attended commemorations in Washington and Shanksville.
Mr Bush and first lady Laura Bush paid their respects at the World Trade Center on Sunday, laying wreaths on the sites of the two towers that collapsed.
At the Pentagon, vice-president Dick Cheney defended the administration's response to the attacks, and praised the US military's conduct of the struggle against terrorism.
"In the conduct of this war the world has seen the best that is in our country. We have shown that Americans are a resolute people - clear in our purposes, steady in difficult tasks.
"We have answered violence with patient justice. We have liberated whole nations from dictatorship, stayed beside them on the path to democracy, and lifted the sights of millions to a future beyond tyranny and terror."
Earlier, former British prime minister Margaret Thatcher joined Mr Cheney at a ceremony at the White House, and took part with secretary of state Condoleezza Rice in a commemoration of non-American victims of September 11th.
"With America, Britain stands in the front line against Islamist fanatics who hate our beliefs, our liberties and our citizens. We must not falter. We must not fail.
"Today we are here to remember to pray for the dead and to share their loved one's grieving. But we also need to renew our resolve that, however bitter or lengthy the struggle, this evil shall not prevail," Lady Thatcher said.
At Shanksville, Mr Bush remembered the passengers on United Flight 93 who rushed the hijackers and forced the aircraft, which had been bound for Washington, to crash, saving an unknown number of lives as they lost their own.
Mr Bush shook hands and expressed condolences with the victims' relatives who came to the rain-swept field near Pittsburgh to mark the anniversary.
The biggest commemoration was at the site of the World Trade Center in New York where victims' relatives laid flowers and prayed while the names of the dead were read out.
At 8.46am, just after the ceremony began, a moment of silence marked the time when the first aircraft struck the north tower.
Further silences followed at 9.03am for when the south tower was hit, and again at 9.59am for when it collapsed, and at 10.29am for when the north tower fell.
String quartets played, a choir sang and jazz trumpeter Wynton Marsalis performed the spiritual song Over in the Glory Land.
New York mayor Michael Bloomberg and his predecessor Rudy Giuliani - who won universal praise for his handling of the rescue and recovery effort five years ago - addressed the New York ceremony.
"Five years have come and gone and we still stand together as one. We come back to this place to remember the heart-breaking anniversary and each person who died here, those known and unknown to us, whose absence is always with us," Mr Bloomberg said.
Mr Bush, who made no public statements during the commemorations yesterday, was due to address the nation last night.
White House officials said his words would be reflective and would reaffirm his commitment to defeating Islamist terrorism.