Divisions among conservative Republicans may leave the GOP unable to block Democrats from including an Obamacare fix that labor unions have demanded in a deal to reopen the government and raise the debt ceiling.

Labor groups want to delay a reinsurance fee they say would raise health care costs for their members.

Republicans are generally opposed to a carve-out for unions, who are among Obama’s staunchest supporters and helped push through Obamacare. But because many conservatives also see the reinsurance fee as a tax, Republicans are in a difficult position. Many suggest they’ll accept the concession to unions, but want other changes in the health care law.

Sen. Chuck Grassley, R-Iowa, said Senate conservatives would find it difficult to swallow any budget deal this week that includes a specific tweak to Obamacare benefitting unions without also delaying the requirement on all individuals to purchase insurance or face a fine.

“That would be a real overreach on the part of Democrats,” Grassley told the Washington Examiner Monday afternoon.

Grassley was quick to say that he is not part of the small group of Senate Republicans consulting with Minority Leader Mitch McConnell, R-Ky, in his negotiations with Majority Leader Harry Reid, D-Nev.

But based on conversations he's had with like-minded conservative Republicans, Grassley predicted any deal that created another Obamacare carve-out without lifting the individual mandate could spark a revolt from the right.

He said that “a senator that has holds on every Obama administration official” could try to filibuster a bill allowing the concession to unions.

Grassley’s colleagues said they believed he was referring to either Sens. Ted Cruz, R-Texas, or Mike Lee, R-Utah, who have led the charge to delay or defund Obamacare in a government funding bill.

Labor unions were among the strongest supporters of the Affordable Care Act when it passed in 2010. But those groups now want changes to the law, claiming it hurts their members and their role in the collectively-bargained, multi-employer insurance accessed by more than 15 million union workers.

Obama, though, has yet to grant the union carve-out despite the administration delaying until 2015 a requirement that all businesses with 50 employees or more offer health insurance or pay steep fines.

In July, union leaders including Teamsters President James Hoffa wrote a letter to Reid and House Minority Leader Nancy Pelosi, D-Calif., warning of “nightmare scenarios” for millions of workers if the law is not changed to accommodate labor health plans.

“Congress wrote this law; we voted for you,” they wrote. “We have a problem; you need to fix it,” they wrote.

After insisting that any deal to reopen the government and raise the debt ceiling would not touch the president's health care law, Democratic leaders are now in the awkward position of pushing for a one-year delay in the Obamacare reinsurance tax.

As part of Obamacare, the tax was supposed to be levied against all insurance plans to share the risk for insurers taking on the sickest patients next year.

The fee is $63 per person covered by an insurance plan per year, so delaying it would protect union insurance plans from taking a major hit just as workers start to use the health law’s insurance exchanges.

Democrats are considering including the union fix in a deal this week to reopen the government and increase the debt ceiling. In exchange, Republicans expect to win a provision that would force Health and Human Services Secretary Kathleen Sebelius to certify that individuals receiving Obamacare subsidies meet a required income level to qualify.

Even though it's a special fix for unions, some Republicans view the re-insurance fee as a tax, making it difficult for them to oppose any effort to delay or repeal the provision.

As long as the re-insurance fee delay would apply to all insurance plans, not just those offered by labor unions, Rep. John Fleming, R-La., said he would be hard-pressed not to support it.

“I understand the unions' problems with the law, especially the 29-hour work week,” he said. “And I consider [the re-insurance fee] a tax, and as long as it would be lifted for all companies, I think it would be good to get it done.”

Still some conservative groups said any deal that includes a fix for unions while keeping the individual mandate intact would be a gift for pro-Obama special interests and further evidence the health care law should be repealed or defunded.

"It is outrageous that rather than stopping Obamacare for the people, Congress is now besieged with lobbyists trying to get carve outs for the politically connected,” said Richard Manning, of Americans for Limited Government.

“This is exactly why Obamacare should be defunded or delayed for every American, not just for those special few who have Gucci-loafered lobbyists with access to the White House and Congressional leaders."