A U.S. senator said Thursday that she will continue to block the promotion of a star Air Force general for granting clemency to a convicted sex offender, a move that is likely to end the commander’s military career.

In a statement for the Congressional Record, Sen. Claire McCaskill (D-Mo.) said she will place a permanent hold on the nomination of Lt. Gen. Susan J. Helms to become vice commander of the Air Force’s Space Command. McCaskill cited the general’s decision last year to erase the sexual-assault conviction of an Air Force captain — an action that emerged as a flash point in the national debate about sex crimes in the military.

Helms became the first U.S. military woman to travel to space in 1993 as a crew member of the space shuttle Endeavour and served as a role model as she climbed to the Air Force’s upper ranks. But her handling of the sexual assault case angered many lawmakers and advocacy groups, who called it emblematic of a flawed military justice system.

McCaskill said Helms’s three-decade military career should be “celebrated,” but added that she has deep concerns about Helms’s decision to grant clemency to the convicted sex offender, a captain at Vandenberg Air Force Base in California who was later discharged from the military.

“With her action, Lt. Gen. Helms sent a damaging message to survivors of sexual assault,” McCaskill said in the statement. “They can take the difficult and painful step of reporting the crime, they can endure the agony involved in being subjected to intense questioning often aimed at putting the blame on them, and they can experience a momentary sense of justice in knowing that they were believed when their attacker is convicted and sentenced, only to have that justice ripped away with the stroke of a pen.”

This undated photo released by the U.S. Air Force, shows Lt. Gen. Susan Helms. Sen. Claire McCaskill (D-Mo.) has put a hold on the nomination Helms, who is tapped to serve as vice commander of the U.S. Space Command. (U.S. Air Force)

McCaskill met privately with Helms last month, but she said her concerns were not allayed.

Court records show that Helms — who is not a judge and did not observe the trial — ignored a recommendation from her legal adviser to uphold the jury’s conviction. The general intervened to grant clemency before an appellate court could hear the case.

Helms did not give a public explanation for her decision. The Washington Post obtained a memo last month that she wrote for her personal files in which she said she found the defendant to be a more credible witness than his accuser.

An Air Force spokesman at the Pentagon declined to comment Thursday and Helms did not immediately respond to a request for comment.