WASHINGTON – House Republicans have scheduled a vote next week on a bill to keep the government open past Sept. 30, but they are still weighing whether to include instructions to defund President Obama’s signature health initiative.

Other details of the legislation have largely been decided, senior Republican aides said Friday. The measure will probably fund the government at current levels through Dec. 15, meaning sharp automatic cuts known as the sequester would remain in place.

Under the proposal, about $20 billion in additional sequester cuts set to hit in fiscal 2014, which begins Oct. 1, would not take effect immediately. But those cuts, which primarily target the Pentagon, could still be implemented in January if Congress fails to reach a broader budget agreement.

Democrats will probably sign off on the legislation if it does not include a rider to defund the Affordable Care Act, commonly known as Obamacare, Democratic aides said. That would defuse the threat of a government shutdown at the end of this month and clear a path for a broader budget debate focused on raising the federal debt limit by the end of October.

A GOP leadership aide said a “clean” bill, without the Obamacare provision, remains a possibility. But House Speaker John Boehner, R-Ohio, and other GOP leaders will not make a final decision, the aide said, until they have a chance to meet with rank-and-file lawmakers, who are due back Monday after a five-week summer recess.

Provoking a fight now over Obamacare would increase the odds of a government shutdown and force Congress to expend additional energy on the budget bill.

On a conference call with lawmakers two weeks ago, Boehner said he would prefer not to turn the budget bill into a full-scale battle over Obamacare. Meanwhile, senior Republicans in the House and Senate have argued forcefully against seeking to defund the program, saying the goal is unobtainable and the strategy could backfire.

Still, outside groups, led by Heritage Action for America, have been stirring grass-roots anger over the health law, and the most conservative Republicans are unlikely to support a budget bill that does not seek to defund the program. That means Boehner could need Democratic support if he chooses to push a “clean” bill.

Rep. Chris Van Hollen of Maryland, the ranking Democrat on the House Budget Committee, said he plans to offer a proposal to replace the sequester cuts, worth about $100 billion in fiscal 2014, with cuts to farm subsidies and the Pentagon and higher taxes on oil companies and the wealthy. But if that fails, as expected, Van Hollen acknowledged that some Democrats might agree to a clean bill that continued the sequester at current levels.

“People will have to decide for themselves what to do if our alternative is defeated,” he said.