US President Barack Obama marked the 9th anniversary of the September 11, 2001 terrorist attacks on Saturday by emphasising national unity and promising that America will be defined by hope rather than fear.
"This is a time of difficulty for our country. And it is often in such moments that some try to stoke bitterness -- to divide us based on our differences, to blind us to what we have in common," Obama said in his weekly radio address.
"But on this day, we are reminded that at our best, we do not give in to this temptation," the president continued. "We stand with one another. We fight alongside one another. We do not allow ourselves to be defined by fear, but by the hopes we have for our families, for our nation, and for a brighter future."
Nearly 3,000 people died on September 11, 2001, when Islamist terrorists flew hijacked planes into the defence headquarters and New York's World Trade Centre towers.
Every year, in New York at Ground Zero, the names of the 2,752 victims who died there are read out against a background of somber music, with moments of silence marking the times when the two airliners slammed into the Twin Towers -- and again when the towers collapsed.
President Obama was to attend the memorial service at the Pentagon, which was also attacked by a hijacked plane. A third service was taking place in Shanksville, Pennsylvania where the fourth hijacked airliner crashed into a field.
The president said that on this day of remembrance, the nation was honouring those who died so that others might live: the firefighters and first responders who climbed the stairs of the burning towers as well as the men and women in uniform who fought to make America safer.
Obama promised that Americans "will never waver in defence of this nation.
"We renew our commitment to our troops and all who serve to protect this country, and to their families." he said. "But we also renew the true spirit of that day. Not the human capacity for evil, but the human capacity for good. Not the desire to destroy, but the impulse to save."