Defense Secretary Chuck Hagel on Monday said US commanders should be barred from overturning criminal convictions, in the wake of anger over a quashed guilty verdict in a sexual assault case.

Under Hagel's proposal, which would have to be approved by lawmakers, commanders would still have the power to alter sentences handed down in court martial cases, defense officials said.

"These changes, if enacted by Congress, would help ensure that our military justice system works fairly, ensures due process, and is accountable," Hagel said in a statement.

The move comes amid mounting concern over sexual assault in the armed forces and outrage in Congress over the case of Lieutenant Colonel James Wilkerson, whose conviction for aggravated sexual assault was overturned by Air Force Lieutenant General Craig Franklin.

The case prompted Hagel to order a review of the military's judicial code, which grants wide-ranging powers to commanding officers who can throw out the findings of juries and judges without explanation.

The military code's provisions, which date back to the founding of the United States, had become outdated as troops that face criminal charges now have access to a "robust" appeals process and professional legal counsel, officials said..

"It became clear that the world had changed," a senior defense official, who spoke on condition of anonymity, told reporters.

In discussions among military leaders and Pentagon lawyers, "there wasn't significant push back" to making the change, the official added.

But the proposal was unlikely to satisfy some lawmakers and advocates for victims of sexual assault, as commanders will still have unquestioned authority to drastically reduce a sentence.

Defense officials said part of the rationale for permitting commanders to retain the power to alter sentences was to allow for plea bargain agreements, which are presided over by commanders.

The Pentagon's proposal also would require commanders to explain in writing any changes made to court-martial sentences.

According to Hagel's proposed changes, commanders would have the power to reverse a verdict only in cases involving minor offenses.

Officials said verdicts are rarely reversed under the current system, with only about one percent of court martial convictions tossed out by commanders.

In the Wilkerson case, Hagel had asked the Air Force to examine whether the military code was correctly applied. And officials said Monday that a review showed the commanding general's decision was in keeping with the military's legal code.

The Air Force, responding to a request from Hagel, also plans to release documents in the case to shed light on why the commanding general threw out the guilty verdict against Wilkerson.

In his statement, Hagel said the Defense Department "still has much more work to do to fully address the problem of sexual assault in the ranks.

"This crime is damaging this institution."