New rules for national security investigations will help protect Americans from terror attacks, FBI Director Robert Mueller told U.S. lawmakers Tuesday, even if they single out people from the Middle East.

Skeptical Democrats clashed with Mueller, who told the House Judiciary Committee that FBI agents would no longer need solid evidence or allegations of wrongdoing to spy on Americans even before opening investigations. Democrats also expressed doubts that the Justice Department and FBI would protect civil liberties and privacy rights after years of previous abuses and stymied congressional oversight.

During nearly two hours of testimony, Mueller described the tentative rules — known as the attorney general's guidelines — as a proactive way to prevent another Sept 11 attack.

The new rules would ensure that suspicious behavior is investigated, Mueller said, citing a July 2001 memo from an FBI agent in Phoenix who noted a rising trend of Middle Eastern men taking flight lessons. The agent's warning was ignored, and the Sept. 11 Commission later said it could have served as a clue to al-Qaida's intent.

"It is that kind of threat and identification of a very suspicious circumstance that would warrant further investigation," Mueller said. Additionally, he said current guidelines make it "very difficult" for agents to look into people believed to be traveling to terror hotspots, such as training camps in Pakistan.

"I believe the American public and this committee want us to understand that potential threat and do what is necessary to try to identify persons who travel to Pakistan, whatever their heritage, whatever their backgrounds, whatever their ethnicity, to determine who is going to Pakistan to obtain that training and may be coming back to the United States," Mueller said.

Rep. Lamar Smith, the panel's top Republican, called Mueller's description a "persuasive argument on the need to change the guidelines."

Democrats sounded unconvinced.

"We're trying to identify what specific safeguards will prevent improper undercover FBI spying ... and improper racial and ethnic profiling," said Judiciary Chairman John Conyers, D-Mich.

"The more I know about them, I'm very concerned about the expanded authority to be given to FBI agents," said Rep. Jerrold Nadler, a Democrat. "We've seen problems before when we gave too much authority to the FBI."

"There are very real questions about how this will operate — not in theory but in practice," said Rep. Artur Davis, a Democrat.

First reported by The Associated Press, the guidelines do not require congressional approval, and the Justice Department wants to have them in place by the month's end. The Justice Department says they will merely streamline existing authorities used in criminal and national security investigation. Critics call them a broad expansion of FBI powers that could result in racial, ethnic or religious profiling.

Mueller is scheduled to make a similar appearance Wednesday before the Senate Judiciary Committee.