A senior Pentagon official who has been under internal investigation, accused of abusive management practices, told his staff Friday he was retiring for health reasons.

Jerry D. Jennings, 65, the deputy assistant secretary of defense for POW/MIA affairs since August 2001, was investigated this year by the Pentagon inspector general for allegations that include reprisals against subordinates and sexual harassment of a female employee. The status of the probe has not been made public and it was not immediately clear Friday what, if any, role it had in Jennings' decision to retire.

Jennings told his staff by letter that he was retiring, effective Saturday.

"It has been my utmost hope to return to full duty; however, my illness precludes my continued service," he wrote. A copy of the letter was released by his spokesman, Larry Greer. Jennings did not specify his illness, and Greer said he had no knowledge of it except that it has kept Jennings away from work since April.

Greer said he did not know the status of the IG investigation.

A spokeswoman for the IG's office, Marine Corps Lt. Col. Rose-Ann Lynch, had no immediate comment. In his letter, Jennings made no reference to the controversy.

"I appreciate your expressions of support during this ordeal," Jennings wrote. "I wish you all continued success as you work this sacred mission."

The Pentagon's POW/MIA accounting effort is far-flung, taking U.S. search teams to remote parts of China, Russia and elsewhere to excavate burial grounds, aircraft crash sites and long-forgotten battlefields.

There are more than 1,800 U.S. servicemen still missing from the Vietnam War, more than 8,100 from the 1950-53 Korean War, about 125 from Cold War spy-related aircraft shootdowns, and 78,000 from World War II. The work sometimes involves sensitive diplomatic efforts with countries like North Korea and Vietnam.

Jennings has been under fire by organizations that represent the interests of MIA families. Early this year the boards of directors of three leading organizations, including the oldest, the National League of POW/MIA Families, each took the unprecedented step of voting "no confidence" in Jennings and urging his removal from office.

"We're all relieved that he's no longer in a position to undercut the seriousness of the U.S. government's commitment or inflict the damage on his own office that has occurred," said Ann Mills Griffiths, executive director of the National League of POW/MIA Families, when asked her reaction to Jennings' resignation.

"His record on the job was very disappointing, unexpectedly so," she added. "We're just thankful that Jennings is no longer in position to obstruct an integrated, thoughtful policy approach to achieve accounting objectives more rapidly."

Although some family groups continued to support Jennings, the most influential faulted him for being unresponsive to their concerns, not working more smoothly with other elements of the government and not pressing harder for foreign cooperation on the MIA issue. They also assert that he has alienated families of the missing and demoralized his staff.

When The Associated Press disclosed the Pentagon's investigation of Jennings last July, he provided a written defense of his record. He wrote that he cooperated fully in the investigation and he declined to comment directly on the accusations, saying the inspector general asked that no one comment until the probe was completed.

Jennings also wrote that he was "aware of the complaints by a small number" of employees and pledged that they would be "handled appropriately."

Jennings held a variety of posts in the Nixon, Ford, Carter, Reagan and Bush administrations from 1973 to 1992 — none related to POW or MIA issues. He was deputy director of the Federal Emergency Management Agency from 1990-92. An official biography says he was a CIA officer from 1965-68.