Biden calls for unity on eve of 9/11 anniversary

US President Joe Biden has called for national unity in a video message released to remember those killed in the September 11, 2001, terrorist attacks in the United States, and to express condolences to their families.

The White House posted the video on its Twitter account on Friday, the eve of the 20th anniversary of the attacks.

Biden said that no matter how much time has passed, commemorations of the attacks "bring everything painfully back as if you just got the news a few seconds ago."

He said that after the attacks, Americans saw "something all too rare, a true sense of national unity. Unity and resilience, the capacity to recover and repair in the face of trauma."

The president said, "Unity is what makes us who we are. America at its best. To me, that's the central lesson of September 11th."

Biden said, "It's that at our most vulnerable, in the push and pull of all that makes us human, in the battle for the soul of America, unity is our greatest strength."

He added, "We find light in the darkness."

Biden plans to visit the scenes of the attacks, including the World Trade Center in New York where hijackers flew two aircraft into its towers.