WASHINGTON — The Senate advanced a sweeping must-pass defense spending bill Wednesday that included a provision to toughen prosecutions of military sexual assaults, although victims' advocates complained the protections did not go far enough.

The annual defense authorization bill, which sets funding and other Pentagon policies, had become entangled in partisan bickering and the growing controversy over the rise in unreported sexual assaults in the military.

A compromise on the defense bill, including the sexual assault provision, was approved late last week in the House. With Wednesday's 71-29 vote in the Democratic-controlled Senate, the package overcame a Republican filibuster threat and is expected to move to final passage this week.

The compromise includes more than 30 new provisions to toughen sexual assault prosecutions. It would strip commanders of their ability to dismiss the findings of a court-martial, establish minimum sentencing guidelines when service members are convicted of sexual assaults, and allow assault victims to transfer out of their units.

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Sen. Kirsten Gillibrand (D-N.Y.) unsuccessfully fought for a provision to change the way assault cases are prosecuted with a proposal that would have reduced commanding officers' role in deciding whether to pursue charges in a reported attack. Cases that are investigated are often dismissed by commanders.

The Gillibrand amendment was backed by the Service Women's Action Network and other organizations, but opposed by military brass and their key allies on Capitol Hill. Opponents said it would weaken the ability of commanders to have total control over their units.

Victims' advocates expressed hope that the bill would nevertheless set the stage for further debate next year on the way the military handles sexual assault prosecutions.

"Our bill does contain groundbreaking reforms that will provide much-needed assistance for victims of sexual assault, while also establishing a climate in the military where there is no tolerance for sexual assault," said Sen. Carl Levin (D-Mich.), chairman of the Armed Services Committee.

The defense bill is usually a bipartisan, popularly supported measure; it has been approved annually for almost 50 years.

It sets Pentagon policy for the year to come, giving troops a 1% pay increase in 2014 and prohibiting the transfer of detainees from the military facility at Guantanamo Bay, Cuba, to the U.S., as some have proposed.

But the core of the debate in Congress this year was over the 35% increase in unreported sexual assaults in the military in recent years.

Gillibrand vowed to continue pressing for tougher regulations next year.

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"The senator will not go away," said Gillibrand spokeswoman Bethany Lesser. "She will keep fighting to protect our brave men and women in uniform and to strengthen our military."

Shortly before advancing the defense measure, the Senate gave final approval to the bipartisan budget accord that could bring a momentary pause to the budget wars and open a new era of political pragmatism in Washington.

President Obama was expected to swiftly sign the budget measure after it cleared the Senate, 64 to 36. All Democrats and nine Republicans supported the deal, which pleased few but was embraced because it reduces the risk of a government shutdown next month.

The $85-billion package negotiated by Rep. Paul D. Ryan (R-Wis.), the former vice presidential nominee, and Sen. Patty Murray (D-Wash.), the budget chairwoman, was modest in scope, but represents an achievement for the divided Congress that has spent the last two years engaged in high-stakes standoffs over government budgets.

lisa.mascaro@latimes.com

Twitter: @lisamascaroinDC