America's top military officers told Congress on Tuesday that sexual assault represented a crisis in the armed forces but warned lawmakers against going too far with legislation stripping commanders of power within the military justice system.

The hearing comes after a wave of sexual assault scandals and new Pentagon data showing a steep rise in unwanted sexual contact, from groping to rape, that have deeply embarrassed the military.

In an exceptional display, the top uniformed officers of the Army, Navy, Marines, Air Force and Coast Guard, along with the chairman of the Joint Chiefs of Staff, all appeared at the Senate Armed Services Committee together to assure Congress they were taking the matter seriously.

The top lawyers from each service sat next to them.

"We are acting swiftly and deliberately to change a climate that has become too complacent," said General Martin Dempsey, chairman of the Joint Chiefs of Staff.

The service chiefs made clear that it was important to maintain the power of commanders, who now have the ability to decide which cases go to trial.

But under proposed legislation by Democratic Senator Kirsten Gillibrand, responsibility for prosecuting sex crimes would be taken out of the victim's chain of command altogether and given to special prosecutors.

General Raymond Odierno, chief of staff of the Army, said that proposal could hurt unit cohesion and noted the importance of the commander to quickly "administer justice."

"Without equivocation, I believe maintaining the central role of the commander in our military justice system is absolutely critical," Odierno said.

Still, many critics of the military's handling of past cases say the system is broken and radical change is necessary.

A study the Defense Department released in May estimated that cases of unwanted sexual contact in the military, from groping to rape, rose 37 percent in 2012, to about 26,000 cases from 19,000 the previous year.

There has been an outcry in Congress over how the military handles such cases, including those in which commanders showed leniency to accused offenders.

In one high-profile case, a senior U.S. military commander in Europe set aside the sexual assault conviction of an Air Force officer, throwing out his one-year prison term and dismissal from the service.

"I cannot overstate my disgust and disappointment over the continued reports of sexual misconduct in the military. We've been talking about the issue for years and talk is insufficient," said Senator John McCain, a Republican from Arizona.

Still, the head of the Armed Services Committee, Senator Carl Levin, a Democrat, appeared sympathetic to military concerns about ensuring the power of the chain of command.

"Only the chain of command can establish a zero-tolerance policy for sexual offenses," Levin said. "Only the chain of command has the authority needed to address any problems with command climate that foster or tolerate sexual assaults."