HOLMDEL, N.J. (AP) - The Bush administration's top anti-terrorism prosecutor said the United States had ample evidence that a devastating terrorist attack on U.S. soil was likely long before Sept. 11.

Assistant Attorney General Michael Chertoff cited nearly a decade's worth of hints that foreign terrorists were targeting Americans, though he did not say there was specific information that could have prevented the attacks.

``As of Sept. 10th, each of us knew everything we needed to know to tell us there was a possibility of what happened on Sept. 11th,'' Chertoff said Friday during a commencement speech to Seton Hall Law School graduates.

On Wednesday, FBI Director Robert Mueller said there may have been missed clues before the attacks and suggested that investigators might have uncovered the plot if they had been more diligent about pursuing leads.

Among the warning signs cited by Chertoff: the bombing of the trade center in 1993; a mid-1990s plan in which an Islamic radical was convicted of plotting to blow up jetliners, New York landmarks and assassinate the pope and fly a small plane into a government building; a death sentence pronounced on Americans by Osama bin Laden in the late 1990s; and the failed millennium bombing plot at Los Angeles International Airport.

``We knew the World Trade Center was a target,'' said Chertoff, who was the U.S. attorney for New Jersey when the trade center was attacked in 1993. ``We knew an airplane could be used as a weapon.''

He said he was not criticizing the country's preparedness, but wanted to help better prepare for coming security challenges. And like other top administration officials, Chertoff said the nation will never be ``100 percent safe.''

``It is never going to happen,'' he said. ``Every bridge, every mall is not going to be 100 percent guarded. Although we must work to achieve perfect security, we can only approach it, not attain it.''

