WASHINGTON &#8212 Weapons of mass destruction, small boats packed with explosives and Islamic radicalization are the greatest terrorist threats facing the country, top U.S. security officials said Monday on the eve of the sixth anniversary of the Sept. 11 terrorist attacks.

The officials told Congress the country is much better prepared to face terror threats than it was then, but terrorists’ desire to attack remains strong.

Homeland Security Secretary Michael Chertoff said the threat of a USS Cole-type attack on U.S. ports – where a small boat packed with explosives detonates in a harbor – is one of his top concerns.

While the department’s goal is to keep nuclear weapons from entering, it also is focusing on how it would respond should a nuclear device get through and explode.

The radicalization of potential new terrorists is another growing concern, the intelligence officials said at the hearing on the nation’s terrorism preparedness. The Internet makes recruiting people to the radical cause much easier.

Despite the confidence expressed by top officials, fewer Americans believe the country is prepared for another attack. A CBS News/New York Times poll taken Sept. 4-9 found that 39 percent of Americans think the country is ready – down from 49 percent a year ago and 64 percent in March 2003 when the war in Iraq began.