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

In a letter to Attorney General 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 the FBI director, Robert Mueller, appears before the panel on September 17.

Judiciary Chairman Patrick Leahy, a Democrat of Vermont., and Senator 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,” Messrs. Leahy and Specter wrote.

They added: “The important aims of the guidelines, and their potential implications for civil liberties, require a meaningful dialogue between Congress and DOJ.”

DOJ stands for the Department of Justice, which oversees the FBI.

The rules are expected to be finalized later this week or early next week. A Justice spokesman, Peter Carr, said yesterday that the department is reviewing the letter.

“We continue to discuss this with Congress, and we are carefully reviewing the suggestions we have received from these discussions,” Mr. Carr said.

The planned changes, first reported last month by the Associated Press, is part of an update of Justice Department policies amid the FBI’s transition from a traditional crime-fighting agency to one whose top mission is to protect America from terrorist attacks.