The Justice Department has agreed to delay new rules giving the FBI greater leeway in investigations of suspected terrorists, deferring to concerns by senators that innocent Americans might be targeted.

In a letter to Senate Judiciary Chairman Patrick Leahy released Thursday, the department said it will postpone the rules until after FBI Director Robert Mueller appears before the panel on Sept. 17.

However, the department still wants to have the rules in place by Oct. 1 to help the FBI more nimbly investigate national security cases, wrote Principal Deputy Assistant Attorney General Keith D. Nelson.

He said that the rules, known as attorney general guidelines, would harmonize multiple and varying sets of standards for how the FBI conducts investigations into one regulation.

Six senators -- including Republican Sen. Arlen Specter of Pennsylvania -- have raised concerns that the rules could target Americans in part based on their race, ethnicity, religion or activities protected by the First Amendment and that these individuals might be singled out without evidence of wrongdoing.

After being briefed about the guidelines over the last several says, the senators this week asked Attorney General Michael Mukasey for a delay until Congress and the public have more time to study them.

"We fully appreciate and share your concern about the potential civil liberties impl traits that, taken together, were deemed suspicious.

Factors that could trigger an inquiry could include travel to regions of the world known for terrorist activity and access to weapons or military training, along with the person's race or ethnicity.