WASHINGTON — Democrats thrust veterans into the center of Congress' contentious health care debate on Thursday, saying the Republican bill replacing the Affordable Care Act could end up marginalizing millions of former service members eligible for medical care at the Department of Veterans Affairs.

"Veterans would end up worse off than they are today under this plan," said Iraq War veteran Sen. Tammy Duckworth, D-Ill. "This is sloppy and irresponsible, and it makes you wonder what else we don't know about this bill."

Congressional Republicans and President Trump have been working for weeks on the new healthcare bill, designed to replace the "Obamacare" law passed by lawmakers in 2010. They've argued the current plan hurts small businesses by forcing them to offer health insurance and infringes on personal freedoms by requiring Americans to buy insurance or pay a tax.

A vote on the new measure was scheduled for Thursday afternoon, but infighting among Republican House members delayed that action.

On Wednesday, White House spokesman Sean Spicer said he wasn't aware of the veterans problem in the bill. House Republican leaders have promised to fix the confusing provisions, but Democrats protesting the bill said it's dangerous to move ahead with the measure without first correcting that problem.

At issue is a change to the GOP-backed bill released on Monday. Officials labeled the alteration as merely a technical correction to the bill, but critics say it also fundamentally changed health insurance benefits for veterans.

Previous versions of the legislation stated that veterans eligible for VA health services but not using them would qualify for a tax credit to help cover the cost of purchasing private-sector health insurance.

But the technical changes dropped that clause. Critics say as written now, the health care bill would block any veteran eligible for VA health services from getting the tax credit, whether they’re actually using VA or not.

Democrats said they’re unsure if the change was intentional or a disturbing oversight.

"This bill keeps getting written and rewritten," said Senate Armed Services Committee Ranking Member Jack Reed, D-R.I. "This provision is going to potentially affect millions of veterans … this whole process has been a disgrace."

Rep. Mark Takano, D-Calif., said he worried the provision could force even more veterans to rely on VA for their primary health care, flooding the already burdened system.

White House officials have repeatedly called the plan a first step in repairing the American health care system, and promised legislative follow-on corrections and additions. Democrats have blasted it as a political stunt that could leave millions of Americans without medical insurance.

About 8 million veterans currently use VA health services, although a large percentage of those visit clinics and hospitals only for specialty care, not all of their medical needs.

Leo Shane III covers Congress, Veterans Affairs and the White House for Military Times. He can be reached at lshane@militarytimes.com.