(This version of the story corrects details of McCaskill-Ayotte bill in the 8th paragraph. The story was first filed on March 6)
WASHINGTON (Reuters) - The U.S. Senate voted down a bill on Thursday seeking to overhaul the way the U.S. military handles cases of sexual assault by giving authority to prosecute sexual assault cases to an independent military prosecutor instead of top commanders.
The bill, sponsored by New York Democratic Senator Kirsten Gillibrand only got 55 of the 60 votes it would have needed to go ahead under Senate rules. The vote was 55-45, with 23 senators crossing party lines.
Immediately after that bill failed, the Senate voted unanimously to advance a separate reform measure that would not go as far as Gillibrand's.
Despite months of intense lobbying, Gillibrand and her supporters could not overcome Pentagon leaders' insistence that such a fundamental change would weaken the chain of command and that officers should have more responsibility, not less, for addressing sex crimes.
"We know the deck is stacked against victims of sexual assault in the military, and today, we saw the same in the halls of Congress," Gillibrand said after the vote, adding that she would continue to press for reforms.
Gillibrand's "Military Justice Improvement Act" had been a focus of intense debate over how the Pentagon should handle assault cases. A study released in May 2013 estimated that incidents of unwanted sexual contact, from groping to rape, had jumped by 37 percent in 2012, reaching 26,000 cases.
The Senate voted 100-0 to proceed with the second bill, sponsored by Democratic Senator Claire McCaskill of Missouri and New Hampshire Republican Senator Kelly Ayotte, who both opposed Gillibrand's legislation.
The McCaskill-Ayotte bill, among other things, would eliminate the so-called good soldier defense, which refers to the ability of a military court to reduce the sentences of troops who are found guilty of sexual assault but have strong military records. It leaves responsibility for prosecution with commanders.
The final vote on the McCaskill-Ayotte bill is expected on Monday.
The Department of Defense has also been struggling to deal with a spate of high-profile cases of sexual assault, including some involving personnel charged with combating the crime.
On Thursday, an Army official said Lt. Col. Joseph Morse, chief of the Army's Trial Counsel Assistance Program and a top sexual assault prosecutor, had been suspended recently pending an investigation into allegations he groped a female colleague.
Also on Thursday, Brigadier General Jeffrey Sinclair pleaded guilty to having an adulterous affair, asking junior female officers for nude photos and possessing pornography on his laptop, although he will fight sexual assault charges.
President Barack Obama in December ordered a year-long review of the military's handling of sexual assault cases.
Several reforms have already been enacted, but Gillibrand pushed to go further. She contended that, among other things, too few victims have been willing to come forward because of the need to deal with the chain of command.
U.S. military leaders opposed her proposal. They said they worried it would weaken the command structure even as they acknowledged an "epidemic" of sexual assaults within the ranks.
Some key members of the Senate, including Carl Levin of Michigan, the Democratic chairman of the Senate Armed Services Committee, also opposed the measure.
Forty-three Democrats, 11 Republicans and one independent voted to go ahead with the bill. Thirty-four Republicans, 10 Democrats and one independent voted against it.