On the eve of the 10th anniversary of the September 11 attacks on Saturday, US President Barack Obama reflected on how the United States had "finally delivered justice" to Osama bin Laden.

Even as US intelligence agencies chased down what officials said is a credible but unconfirmed threat of an Al-Qaeda attack around the September 11 commemorations, he also said America would never "waver" in the face of danger.

"Today, America is strong and Al-Qaeda is on the path to defeat," Obama said in his weekly Internet and radio address.

"Even as we reflect on a difficult decade, we must look forward, to the future we will build together.

"That includes staying strong and confident in the face of any threat," Obama said.

"We've taken the fight to Al-Qaeda like never before. Over the past two and a half years, more senior al Qaeda leaders have been eliminated than at any time since 9/11," Obama said.

"And thanks to the remarkable courage and precision of our forces, we finally delivered justice to Osama bin Laden."

Bin Laden was killed in a daring US special forces raid on his compound in Abbottabad, Pakistan in May, after nearly 10 years on the run after ordering attacks on Washington and New York in 2001 that killed nearly 3,000 people.

"A decade after 9/11, it's clear for all the world to see -- the terrorists who attacked us that September morning are no match for the character of our people, the resilience of our nation, or the endurance of our values," Obama said.

"They wanted to terrorize us, but, as Americans, we refuse to live in fear. Yes we face a determined foe, and make no mistake -- they will keep trying to hit us again."

"But as we are showing again this weekend, we remain vigilant. We're doing everything in our power to protect our people. And no matter what comes our way, as a resilient nation, we will carry on."

Obama will Sunday visit the Ground Zero site of the felled World Trade Center Towers, the Pentagon outside Washington and Shanksville, Pennsylvania where a fourth jet used in the attacks was downed by hero passengers.

"Ten years ago, ordinary Americans showed us the true meaning of courage when they rushed up those stairwells, into those flames, into that cockpit," he said.

"In the decade since, a new generation has stepped forward to serve and keep us safe. In their memory, in their name, we will never waver.

"We will protect the country we love and pass it safer, stronger and more prosperous to the next generation."