WASHINGTON » Congressional Republicans vowed Thursday to toughen President Barack Obama’s day-old legislation to authorize military force against Islamic State fighters, and House Democratic leader Nancy Pelosi warned, "It’s going to be hard" to find common ground.

Nothing underscored the yawning divide between the two parties more than Obama’s request to bar "enduring offensive combat operations" from the struggle against terrorists who have seized territory in Syria and Iraq and beheaded hostages.

House Speaker John Boehner, R-Ohio, said disapprovingly that Obama’s proposal would "tie his hands even further" than current law.

But Pelosi, recalling the long, difficult war in Iraq, said the president "has to be commended" for proposing to limit his own power.

Obama is seeking a three-year authorization for the use of force against the Islamic State militants or any successor groups, without regard to international boundaries. His proposal would leave in place 2001 legislation approving military action against al-Qaida following the terror attacks of 9/11.

At the same time, the president would repeal legislation passed in 2002 in the run-up to the invasion of Iraq. As for ground combat operations, Obama says he does want flexibility allowing rescue missions, intelligence collection and the use of special operations forces in possible military action against Islamic State leaders.

Failure to pass any legislation would mark a significant political defeat for Obama, with unpredictable consequences overseas at a time of expansive terrorist threats, a confrontation between the West and Russia over Ukraine and international negotiations with Iran over its nuclear program.

Boehner was among several Republicans who said the president’s plan wasn’t up to the job of defeating Islamic State forces.

"I want to give our military commanders the flexibility and the authority that they need to defeat our enemies," he said. "And that’s exactly what Republicans will make the case for as we move through rigorous hearings and oversight on this issue."

Officials said Boehner’s concern was stoked in part by statements from administration officials saying that Obama envisions more limits in the current struggle than in the one launched after terrorists hit the World Trade Center and Pentagon in 2001.

While Obama’s legislation landed in Congress with a thud Wednesday, some senior lawmakers appeared to be trying to create room for an eventual compromise.

The Senate’s three top Democrats, Harry Reid of Nevada, Dick Durbin of Illinois and Chuck Schumer of New York, have all refrained from commenting since the proposal was released, an unusual silence on an issue of such significance.

And Sen. Bob Corker, R-Tenn., chairman of the Foreign Relations Committee, said he hoped for a bipartisan measure to emerge.

Administration officials are expected to testify at hearings in support of the president’s proposal, beginning after next week’s scheduled congressional vacation. There is no announced timetable for a vote in either house.

Boehner, like other Republicans, said Obama has yet to produce an "overarching strategy" to deal with a terrorist threat.

Rep. Ed Royce, R-Calif., referring to U.S.-led airstrikes against Islamic State fighters in Iraq and Syria, said the "campaign isn’t pummeling the enemy as it should."

"Congressional authority is of no value if the president isn’t willing to act decisively," added the chairman of the House Foreign Affairs Committee.

There was fresh criticism from Democrats, as well, but from the other direction.

Sen. Ben Cardin of Maryland noted that the proposal would leave in place the authorization for the use of force approved against al-Qaida after the terror attacks of Sept., 11, 2001. If lawmakers concur, he said, "Congress could be authorizing a state of perpetual war, and giving this president and future presidents a blank check to keep America at war."

Another Democrat, Rep. Brad Sherman of California, said the administration’s proposed limitation on ground troops was not strong enough. "’Enduring offensive ground operations’ is a highly elastic phrase which the next president may interpret broadly," he said.

Freshman Rep. Seth Moulton, D-Mass., a Marine veteran who served four tours in Iraq, said, "I am not ready to support an authorization for military force until the administration presents a comprehensive strategy to ensure long-term success."

Pelosi underscored the extent to which the war in Iraq is influencing Democrats.

Recalling legislation sought for that war by President George W. Bush, she said she voted against the measure even though she had been warned it might mean the end to any thoughts she had of entering the party’s leadership.

In the end, she said, "some Democrats voted for it. They have said, ‘I wish I hadn’t.’"