U.S. President Barack Obama on Thursday urged Americans to reclaim the spirit of unity that was seen in the wake of the Sept. 11, 2001 terrorist attacks, at a time when people in Washington and across the country are in heated debates as to where the U.S. should be heading.

"The worst terrorist attack in American history also brought out the best in our country," Obama wrote in an op-ed published on Thursday's USA Today, recalling the times when firefighters, police, volunteers and ordinary Americans came together and helped each other after nearly 3,000 people were killed in the attacks in New York City, the Pentagon and Shanksville, Pennsylvania, on Sept. 11, 2001.

"We were united, as Americans," he wrote. "This is the true spirit of America we must reclaim this anniversary -- the ordinary goodness and patriotism of the American people and the unity that we needed to move forward together, as one nation."

The president made the request when Democrats and Republicans in Washington are vigorously debating about how to deal with the challenges the nation is facing -- lackluster economic growth, stubbornly high jobless rate and huge debt and deficit.

Obama is set to deliver a speech to a joint session of Congress Thursday night, offering a package of ideas to revive job creation.