The State Department's security chief announced his resignation on Wednesday in the wake of last month's deadly Blackwater USA shooting incident in Baghdad and growing questions about the use of private contractors in Iraq.

Richard Griffin, the assistant secretary of state for diplomatic security, announced his decision to resign at a weekly staff meeting, according to an internal informational e-mail sent to colleagues.

"He read his letter of resignation at the weekly Diplomatic Security staff meeting," said the e-mail, which was read to The Associated Press by one its recipients. "There was no detailed reason provided and no effective date identified at this time."

Neither Griffin nor spokesmen for the department's Bureau of Diplomatic Security could be reached for immediate comment.

It was not clear if Secretary of State Condoleezza Rice had or would accept Griffin's resignation.

Griffin announced his resignation just a day after Rice ordered a series of measures to boost government oversight of the private guards the department uses to protect its diplomats in Iraq.

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.

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.

Rice's review 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," their report said.

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.