Biden said the US was united in the days following the September 11 attacks.
"To me, that's the central lesson of September 11th: Unity is our greatest strength," he said on Friday.
Biden and First Lady Jill Biden will travel to three sites of the attack on Saturday.
See more stories on Insider's business page.
President Joe Biden called for unity ahead of the 20th anniversary of 9/11, citing the cooperation that emerged days after the unprecedented terror attacks.
"In the days that followed September 11, 2001, we saw heroism everywhere in places expected and unexpected. We also saw something all too rare: national unity," Biden said.
He added: "To me, that's the central lesson of September 11th: Unity is our greatest strength."
Biden paid tribute to the almost 3,000 people who died in the attack.
"To the families of the 2,977 people from more than 90 nations killed on September 11, 2001, in New York City, Arlington, Virginia, and Shanksville, Pennsylvania, and the thousands of more that were injured, America and the world commemorate you and your loved ones," Biden said.
"We honor all those who risked and gave their lives in the minutes, hours, months, and years afterward," he added.
Biden also addressed the "fear and anger, resentment and violence against Muslim Americans" that followed the attacks.
On Saturday, Biden and First Lady Jill Biden will travel to all three sites of the attacks.
They'll first visit lower Manhattan to honor the 2,763 people who died when the World Trade Center collapsed. Their next stop will be Shanksville, PA, to pay tribute to the 40 passengers and crew of United Airlines Flight 93, who died while thwarting hijackers from crashing the plane into the US Capitol.
They will also visit the Pentagon, where 184 people died after American Airlines Flight 77 crashed into the building.
"No matter how much time has passed, these commemorations bring everything painfully back as if you just got the news a few seconds ago," Biden said in his speech.