Washington - Ambitious legislation to stanch the growing number of sexual assaults in the armed forces by overhauling the military justice system faces an uncertain future due to objections from senior Defense Department leaders and key members of Congress who are concerned the proposed changes go too far.

The bill crafted by Sen. Kirsten Gillibrand, D-N.Y., cleared an important hurdle Tuesday when the Senate Armed Services personnel subcommittee, for which she is chairwoman, approved the measure. But the legislation must get through the full committee and its chairman, Sen. Carl Levin, D-Mich., has signaled his intent to offer an alternative that would mute the most aggressive reforms in Gillibrand's bill.

Her legislation would remove commanders from the process of deciding whether serious crimes, including sexual misconduct cases, go to trial. That judgment would rest instead with seasoned trial lawyers who have prosecutorial experience and hold the rank of colonel or above. Her bill also would take away a commander's authority to convene a court-martial. That responsibility would be given to new and separate offices outside the victim's chain of command.

But Levin and other lawmakers, echoing the Joint Chiefs of Staff, believe that cutting commanders out of the legal process would undermine their ability to enforce order and discipline within the ranks.

The Armed Services Committee is scheduled to meet today to vote on the provisions that will be included in a sweeping defense policy bill for the 2014 fiscal year that begins Oct. 1.

Levin's alternative, which has bipartisan support, would require a review by an individual higher up in the chain of command if a commander decides not to prosecute a sexual assault case. It would make it a crime to retaliate against victims who report a sexual assault and it would relieve commanders of their responsibilities if they do not create a climate receptive for those who report crimes.

Sen. Lindsey Graham, R-S.C., the personnel subcommittee's top Republican, said commanders shouldn't be sidelined from sexual assault cases. "I don't think you quite resolve a problem in the military without the chain of command buying into it and being held more accountable," he said.

But frustration over the Defense Department's failure to to eradicate sexual assaults is driving support for substantive changes.

Sen. Patrick Leahy, D-Vt., Senate Judiciary Committee chairman, said Tuesday at a separate hearing that Congress is considering stripping the military of its authority to prosecute sexual assaults, shifting responsibility to state prosecutors.

Leahy said that while the proposal is controversial, it would send a message that doing "things as they've always been done is not acceptable."

The Pentagon estimated in a recent report that as many as 26,000 military members may have been sexually assaulted last year, up from an estimated 19,000 assaults in 2011.

By week's end, the House is scheduled to vote on its version of a defense policy bill that would take away the power of military commanders to overturn convictions in rape and assault cases.