The Pentagon said Monday that it would ask Congress to change military law so that commanders can no longer overturn convictions without explanation, a proposal that follows a public outcry over the handling of some sexual-assault cases.

Defense Secretary Chuck Hagel said he wanted to take away senior commanders’ long-standing authority to toss out jury verdicts after a court-martial but before the case can be heard on appeal. While commanders could still reduce or even eliminate sentences, under Hagel’s proposal they would have to justify their actions in writing for the first time and could not set aside convictions in major cases.

“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.

Hagel’s action was prompted by the response to an Air Force general’s decision in February to grant clemency to a fighter pilot who had been convicted by an all-male military jury of sexually assaulting a woman while she slept in his guest bedroom.

The commander, Lt. Gen. Craig A. Franklin, who is not a judge and did not observe the trial, gave no explanation, infuriating lawmakers and advocacy groups who said the outcome would discourage other victims from reporting sexual abuse. The defendant in the case, Lt. Col. James Wilkerson, was freed from the brig and has returned to active duty.

Military leaders have long resisted any proposed changes to the Uniform Code of Military Justice that would reduce senior commanders’ virtually unlimited authority to reduce or overturn sentences before a case can be heard on appeal.

Last month, the judge advocate generals from each of the armed services told a Senate panel that senior commanders have prized that authority for generations, finding it a crucial tool to uphold “good order and discipline” in their units.

Guilty verdicts are set aside by a senior commander, known as a convening authority, only in rare cases — about 1 percent of the time, military officials said. It is more common for a sentence to be modified or reduced.

Hagel, however, has taken a different stance from the armed services. Shortly after taking office in late February, he ordered the Pentagon’s lawyers to review military law and made clear that he wanted changes.

“He directed that we take a very serious look without blinders on,” a senior defense official involved in the review told reporters Monday, speaking anonymously under conditions set by the Pentagon.

Hagel also ordered a review of the Air Force sexual-assault case. Details have not been made public, but the senior defense official said that Franklin acted within his authority and that his decision cannot be changed.

Several lawmakers who had criticized the Air Force and other services for their handling of sexual-assault cases welcomed the Pentagon’s proposal to modify military law.

“A commander who has not listened to the testimony should not be able to unilaterally overturn a jury verdict or change an offender’s sentence without explanation — and it’s great news that Secretary Hagel agrees,” Sen. Claire McCaskill (D-Mo.) said in a statement.

The change would apply to all cases that result in guilty verdicts at court-martial, not just sexual-assault prosecutions.

Some advocacy groups said Hagel’s proposal did not go far enough.

Anu Bhagwati, executive director of the Service Women’s Action Network, commended Hagel but said the Pentagon needed to further reduce the power of senior commanders over the military justice system and give more authority to prosecutors and judges.

“Unless pretrial decision making around investigation and prosecution of offenses is also removed from the hands of commanders and given to impartial prosecutors, military criminal justice will remain a lesser form of justice,” she said.