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(NBC NEWS) -- Sen. John McCain, who built a potent political career on his record as a Vietnam veteran and ex-prisoner of war, on Tuesday told the leaders of every military branch he cannot in good conscience advise women to join the service as the military grapples to contain and curb its sexual assault epidemic.

"Just last night, a woman came to me and said her daughter wanted to join the military and could I give my unqualified support for her doing so. I could not," McCain, an Arizona Republican, said during a Senate Armed Services Committee hearing examining whether all serious sexual crimes should be removed from the chain of command.

"At its core, this is an issue about defending basic human rights but it's also a long-term threat to the strength of our military. We have to ask ourselves: if left uncorrected, what impact will this problem have on recruitment and retention of qualified men and women?" McCain asked. "I cannot overstate my disgust and disappointment over continued reports of sexual misconduct in our military. We've been talking about this issue for years and talk is insufficient."

The pivotal hearing follows numerous calls for a military-justice overhaul amid a recent barrage of sexual misconduct allegations in the ranks - including separate sex-assault charges against two branch leaders tasked with preventing rapes. In May, the Pentagon released an annual report estimating as many 26,000 military members faced unwanted sexual contact in 2012 - an increase from 19,000 cases the previous year. The numbers were based on an anonymous survey of military personnel.

And while he and his fellow four-star generals and admirals said they remain open to any idea to help stem the crisis, Army Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, maintained that discipline and punishment of sex offenders in the ranks must stay inside the chain of command.

"The role of the commander should remain central. Our goal should be to hold commanders more accountable not render them less able to help us correct the crisis," Dempsey said. "The commanders' responsibility to preserve order and discipline is essential to effecting change."

Under questioning from McCain, however, Dempsey acknowledged that the armed forces allow, albeit unwittingly, some people with histories of sexual bad acts to enlist and serve.

"There are currently, in my judgment, inadequate protections for precluding that from happening," Dempsey said. "So a sex offender could, in fact, find their way into the armed force of the United States, and in fact there are cases where a conviction (of a sex crime committed while in the service) wouldn't automatically result in a discharge."

"Obviously," McCain responded, "we have to fix that."

Dempsey - again at the behest of senators - also agreed to launch an immediate change in how the Pentagon tracks sexual misconduct within the ranks by dividing its accounting of such offenses between rapes and sexual harassments.

Despite the Pentagon's own analysis that some 26,000 military members faced unwanted sexual contact during 2012, Sen. Claire McCaskill, D-Mo., said nobody at the Department of Defense can offer an accurate number on how many women and men in the service are raped. Her reason: in its annual report on sex assaults, the Pentagon combines criminal attacks and unwanted gazes in the same column of numbers.

"You have all mushed together two issues," McCaskill said. "You have two problems: one, you have sexual predators who are committing crimes and two, you have work to do on the issue of a respectful and healthy work environment. These are not the same issues.

"'Unwanted sexual contact' (as the Pentagon report defines it) is everything from somebody looking at your sideways when they shouldn't to pushing you up against the wall and brutally raping you ... We need to know how many women and men are being raped on an annual basis and we have no idea right now," she said.

Sen. Kirsten Gillibrand, a New York Democrat, put it to assembled leaders of the Army, Navy, Marines, Air Force and Coast Guard this way: "Not every single commander can distinguish between a slap on the ass and a rape."

Sen. Carl Levin, D-Mich., chairman of the armed services committee, instructed Dempsey to have the Pentagon install a system that surveys and calculates sexual misconduct by both the frequency of rapes and of sexual harassments.

Dempsey agreed.

"Here's how we got here," Dempsey said. "Ten, 12, 15 years ago, there was a conversation about whether we should separate these categories. Because in separating them, (some felt) you could encourage some to ignore the unwanted sexual touching or the sexual harassment and focus in only on the sexual assault.

"It was our view 15 years ago, this problem was a continuum, not individual acts. I'm suggesting to you we didn't get to this point by being stupid," Dempsey added. "We actually got to this point because we were trying to do the right thing. Looking back on it, it's probably time to adjust it."

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