WASHINGTON (AP) — The Republican-controlled House of Representatives approved a $585 billion defense policy bill that grants President Barack Obama the authority to expand the U.S. military campaign against Islamic militants in Iraq and Syria despite misgivings about a new American combat role after more than a decade of war.

The vote on Thursday was 300-119, a reflection of the popularity of the sweeping, bipartisan measure that authorizes funds for American troops as well as ships, planes and other war-fighting equipment built in congressional districts nationwide.

The measure heads to the Senate where passage is expected next week, although some Republican senators are angry over the bill's unrelated provisions to expand wilderness areas.

The legislation endorses Obama's latest request to Congress in the 4-month-old war against extremists who brutally rule large sections of Iraq and Syria. The bill provides $5 billion for the stepped-up operation of air strikes and the dispatch of up to 1,500 more American troops.

It also reauthorizes the Pentagon plan to train and equip moderate Syrian rebels battling the forces of President Bashar Assad, with that mandate expiring Dec. 11. The legislation would extend that authority for two years.

Still, war-weary lawmakers expressed considerable unease about a slippery slope for the American military after years of conflicts in Afghanistan and Iraq.

"We're getting more deeply involved in the war in Iraq and Syria," complained Rep. Jim McGovern, a Democrat.

The top Democrat on the House Armed Services Committee, Rep. Adam Smith, insisted that U.S. involvement was limited.

"The train and equip mission is just that," Smith said. "I don't want U.S. combat troops fighting this ground war .... By training and equipping the Syrians and Iraqis, we can empower them to fight their own ground war with our support from the air."

Unity on a new legal justification for U.S. military operations against the extremists remains elusive in Congress, underscored by the divisions displayed across the Capitol.

Democrats on the Senate Foreign Relations Committee sought to push through a measure defining how Obama can use military force in Iraq and Syria. But Republicans, who are generally supportive of the war, rebelled. They objected to a lack of debate and legislative maneuvering.

House Speaker John Boehner, a Republican, reiterated his call for Obama to submit a proposal to Congress for a new authorization.

The bill would provide the core funding of $521.3 billion for the military and $63.7 billion for overseas operations in Afghanistan and Iraq. Despite Obama's objections, the measure maintains the prohibition on transferring terror suspects from the federal prison at Guantanamo Bay, Cuba, to the United States.

The Pentagon sought cuts in military benefits. Lawmakers compromised by agreeing to make service members pay $3 more for co-pays on prescription drugs and trimming the growth of the off-base housing allowance by 1 percent instead of the Pentagon's deeper 5 percent recommendation.

The legislation would change the military justice system to deal with sexual assault cases, including scrapping the nearly century-old practice of using a "good soldier defense" to raise doubts that a crime has been committed.

The measure would give accusers a greater say in whether their cases are litigated in the military or civilian system and would establish a confidential process to allow victims to challenge their separation or discharge from the military.

Officials said Thursday that the number of sexual assaults reported by military service members increased 8 percent in 2014, suggesting victims are far more willing to come forward and seek help or file complaints than in years past.