Richard Griffin, the Assistant Secretary of State for the Bureau of Diplomatic Security, announced his decision to step down at a weekly staff meeting, State Department spokesman Sean McCormack said, adding that Secretary of State Condoleezza Rice accepted the resignation, which is effective Nov. 1.
"Secretary Rice is grateful to Ambassador Griffin for his record of long exemplary service to the nation," McCormack said. "He has distinguished himself during a 36-year career with the U.S. government, serving in some of the most sensitive and demanding posts."
Griffin, an ambassador-rank official who previously held senior posts with the Secret Service and Veteran's Affairs Administration, had been in his current position since June 2005.
His resignation letter to President Bush and copied to Rice made no mention of the Blackwater or other security matters involving Iraq, saying only that he was going to "move on to new challenges," according to a copy provided to The Associated Press.
He will be replaced on an acting basis by one of his deputies, Gregory Starr, McCormack said.
Neither Griffin nor spokesmen for the department's Bureau of Diplomatic Security could be reached for comment.
His resignation comes amid rising criticism from Iraqis and the U.S. Congress of the State Department's reliance on private security guards and the rules they operate under.
Just a day earlier, Rice accepted ordered a series of measures to boost government oversight of the private guards the department uses to protect its diplomats in Iraq, including more explicit rules on when and how to use deadly force.
The steps were recommended by a review panel Rice created after a Sept. 16 incident in which Blackwater personnel are accused of killing 17 Iraqi civilians. The panel found serious lapses in the department's oversight of such guards, who are employed by Griffin's bureau.
"Prompt measures should be taken to strengthen the coordination, oversight and accountability aspects of the State Department's security practices in Iraq in order to reduce the likelihood that future incidents will occur," the panel said in its 24-page report.
The panel, however, did not single anyone or any agency out for criticism.
Arguments on Capitol Hill over the role of private contractors in wartorn Iraq have largely obscured the broader debate over the war in recent weeks as majority Democrats have scrambled for new strategies designed to end the U.S. presence there.
In addition to clarifying the rules of engagement, Rice accepted recommendations from the panel for private security guards to undergo cultural awareness and Arabic-language training and to set up a board to investigate any incidents where they use deadly force.
Rice had already accepted interim suggestions from the panel to have Diplomatic Security agents escort diplomatic convoys protected by Blackwater and other private guards, install cameras in all security vehicles, improve communications with U.S. military forces in areas where they travel, and record and catalogue radio traffic with the embassy.
The panel made no specific recommendations about what should happen to Blackwater, whose guards were escorting an official from the U.S. Embassy when the shooting occurred. Iraqi authorities claim Blackwater guards fired unprovoked, but Blackwater's founder has said his employees were fired on first.
The panel recommended that when a separate FBI review of the incident is complete the U.S. embassy in Baghdad should assess "whether the continued services of the contractor involved is consistent with the accomplishment of the overall mission in Iraq."
The killings have outraged Iraqis and focused attention on the shadowy rules surrounding heavily armed private guards.
The Iraqi government is demanding that Blackwater be expelled from the country within six months and that its employees be subject to Iraqi law.
The moves announced Tuesday are among those that Rice opted to make on her own, but further changes are likely after she meets later this week with Defense Secretary Robert Gates.