As his country prepares to mourn the victims of the September 11th attacks, US President Joe Biden has called for togetherness.
He paid respect to the 2,977 individuals who died in a video broadcast on the eve of the 20th anniversary.
"We honor all those who risked and gave their lives in the minutes, hours, months, and the subsequent years," President Biden said in the video, speaking to the emergency workers who responded to the attacks.
Commemoration ceremonies are due to take place on Saturday.
"No matter how much time has passed, these commemorations bring everything painfully back as if you just got the news a few seconds ago," he added.
He acknowledged the "darker elements of human nature - fear and wrath, hatred and violence towards Muslim Americans" that arose in the aftermath of the attacks, but stated that unity remained the US' "greatest strength."
"We learned that the one thing that must never be broken is unity," he continued.
Meanwhile, British Prime Minister Boris Johnson stated that the assaults had failed to "break our trust in freedom and democracy." 67 Brits were killed in the 11 September attacks.
The strikes, which were orchestrated from Afghanistan by al-Qaeda, saw four US passenger aircraft hijacked by suicide bombers, two of which were flown into New York's World Trade Center Twin Towers.
President Biden is scheduled to conduct commemorations on Saturday, and he will accompany first lady Jill Biden to the three assault sites.
There will also be six moments of silence to mark the periods when the two World Trade Center towers were hit and fell, as well as the hours when the Pentagon was attacked and Flight 93 crashed.
The commemorations come at a difficult moment for the president, who has faced harsh criticism in recent weeks over the United States' departure from Afghanistan, which ended a US presence that began less than a month after the September 11 attacks.
Biden had vowed to depart Afghanistan before the 20th anniversary of the assaults and had stated that the Taliban would be unlikely to regain control of the nation.
Instead, the militants moved from seizing control of their first major city to seizing control of the capital in less than ten days.