Washington (CNN) -- President Barack Obama's request for FBI Director Robert Mueller to stay on for another two years takes an important step Wednesday, when the Senate Judiciary Committee holds a hearing on what could be a precedent-setting job extension.
Mueller's term ends September 4, exactly a decade after he took the job as director of the FBI. Under current law, an FBI director may serve no more than 10 years, but Obama wants the law changed to allow Mueller to serve a total of 12 years.
The White House has said it needs continuity in national security at the FBI while changes are taking place at the CIA and Pentagon.
Scheduled witnesses for Wednesday's hearing include Mueller; former Deputy Attorney General James B. Comey; William W. Van Alstyne, professor at William & Mary Law School; and John C. Harrison, professor at University of Virginia School of Law.
Capitol Hill staffers have expected lawmakers to approve the extension quickly and quietly before they leave for their August break.
But scattered grumbling by some agents and legislative concerns about establishing a precedent loom.
Sen. Chuck Grassley, R-Iowa, has said he is "open" to the extension. But he said he sees "a risky precedent" and urged a hearing on the issue.
The FBI Agents Association, an organization of rank-and-file agents, said it stands by its May 12 statement backing the two-year extension.
However, FBI Agents Association President Konrad Motyka noted the irony of Mueller staying on while FBI supervisors -- under a Mueller policy -- can be forced out after seven years if they are not promoted.
"In petitioning to extend Director Mueller's term, President Obama cited the need for stability," Motyka said. "Likewise in these extraordinary times, the FBIAA is renewing its call upon the director to terminate the "up or out" policy, a program with negative consequences for continuity and stability," Motyka said.
One agent said there's a wide range of views on FBI management and policy.
"I can tell you I think the majority of FBI agents are frustrated or even angry about various policies or practices, but that doesn't mean they're aimed at Director Mueller," the agent said.
"The number of agents who would want him replaced is much lower," said the agent, who requested anonymity because he was not authorized to comment.
FBI and Justice Department sources have acknowledged a lingering resentment among some longtime agents resistant to changes pushed by the hard-charging director. But other officials point to the "up or out" policy as an example of change needed to help transform the FBI into a more modern, efficient organization with a focus on counterterrorism.