WASHINGTON (AP) — New rules on FBI investigations of national security cases should be delayed, top Senate Judiciary Committee members said Monday, raising concerns that ethnic or racial groups could be targeted despite no evidence of wrongdoing.

In a letter to Attorney General Michael Mukasey, the senators called for congressional hearings on the rules before they are finalized. They suggested delaying the rules — known as the attorney general guidelines — until FBI Director Robert Mueller appears before the panel Sept. 17.

Judiciary Chairman Patrick Leahy, D-Vt., and Sen. Arlen Specter of Pennsylvania, the panel's top Republican, called the guidelines a "laudatory effort to ensure that front-line agents are given clear rules to follow in pursuit of their investigations."

"Nevertheless, efforts to harmonize the rules governing criminal and national security matters also raise potential civil liberties concerns, given the broader latitude currently given to investigators to consider race and ethnicity in national security matters," Leahy and Specter wrote.