President Joe Biden used the 10th anniversary of the raid that killed Osama bin Laden -- "a moment I will never forget" -- to reaffirm his decision to remove all US troops from Afghanistan.

"We followed bin Laden to the gates of hell -- and we got him," Biden said in a statement released by the White House. 

"We kept the promise to all those who lost loved ones on 9/11: that we would never forget those we had lost, and that the United States will never waver in our commitment to prevent another attack on our homeland."

Biden, who announced last month that he would end Washington's longest war by September 11, praised then-president Barack Obama for his 2011 decision to approve the secret operation targeting the al-Qaeda leader, and praised the special forces who carried it out in Pakistan.

Watching the operation remotely from a crowded White House Situation Room, Biden said, was "a moment I will never forget -- the intelligence professionals who had painstakingly tracked him down; the clarity and conviction of President Obama in making the call; the courage and skill of our team on the ground."

Now, as the US begins pulling the last of its troops from Afghanistan, Biden said: "Al Qaeda is greatly degraded there. But the United States will remain vigilant about the threat from terrorist groups that have metastasized around the world. 

"We will continue to monitor and disrupt any threat to us that emerges from Afghanistan. And we will work to counter terrorist threats to our homeland and our interests in cooperation with allies and partners around the world."