Just as it failed to heed the warning signs of Adolf Hitler's aggression in the 1930s, the United States did not do enough to prepare for terrorist attacks in the 1990s, Rudolph Giuliani told his former colleagues Saturday.

"This is going to stand as a reminder to us to never let our guard down again," the former mayor of New York said of the Sept. 11 terrorist attacks.

He delivered a morning speech at the U.S. Conference of Mayors, which for the first time split its annual meeting between Washington and New York.

Giuliani's successor, Michael Bloomberg, attended the conference on Friday but skipped Saturday's session to go to Washington for the annual Alfalfa Club dinner, which features hundreds of Washington's top power brokers from both political parties.

The Alfalfa Club dinner is a private, off-the-record gathering and is closed to the press.

The mayors were taken on a tour to the World Trade Center disaster site.

"It's overwhelming," said Madeline Cain, mayor of Lakewood, Ohio, a town of 58,000 near Cleveland. "America is recovering from this, but this city and these people who are here everyday, I don't know how you recover from this. How do you go home?"

It was the first trip to the disaster site for former New York City police commissioner and current Houston Mayor Lee Brown. "I often reflect on the many people I knew [who died on Sept. 11]," Brown said. "It really is so unbelievable that something like this can happen."

At a luncheon, Sen. Hillary Rodham Clinton told the mayors she has sponsored legislation that would provide $3 billion in funding to communities called the Homeland Security Block Grant. The legislation would finance additional police, fire and other security protection.

"We want to provide our men and women in uniform with every tool necessary to rout out and defeat the terrorist network wherever they can be found," she said. "I think homeland security deserves the same consideration."

Giuliani said the United States needs to remain vigilant against terrorism.

"In the 1930s, Hitler told us what he was going to do and we ignored it for years and years and years," Giuliani said. "In the 1990s, the terrorists told us what they were going to do and we ignored it. We glorified Yasser Arafat when he was training terrorists in Palestine. We allowed Saddam Hussein to build weapons of mass destruction as we removed inspectors.

"And we ignored — I can't say the handwriting on the wall — but maybe the handwriting just in the desk drawer that just needed to be opened. And we should never do that again."