Delegates to the AFL-CIO convention in Los Angeles approved a resolution Wednesday calling for major changes to the Affordable Care Act, also known as Obamacare.

The resolution passed by voice vote despite furious lobbying from White House officials calling on Big Labor leaders to table the resolution.

The resolution states: "The ACA should be administered in a manner that preserves the high-quality health coverage multi-employer plans have provided to union families for decades and, if this is not possible, we will demand the ACA be amended by Congress."

The resolution put the nation's largest organized labor federation, representing more than 12 million workers, on record saying that President Obama's health care law is harming their existing health insurance.

Terry O'Sullivan, president of the Laborers' International Union of North America, said in a speech on the convention floor that, if the administration could not address their concerns, then organized labor should call for the law's full repeal.

“[To] the men and women that I represent, it could have a devastating impact on our ability to provide health insurance to them and their families," O'Sullivan told the Nation.

The vote is a major embarrassment to the administration. Prior to the law's passage, Obama had repeatedly promised it would not harm existing employer-provided insurance.

It is an embarrassment to many union leaders as well. They had urged their members to support the president's legislation and praised it after its passage.

The labor leaders had done so with the tacit understanding that the administration would later fix potential problems with the legislation regarding union-backed multi-employer health care plans. The fixes never came though, leaving many leaders in a difficult position with their members.

International Association of Fire Fighters President Harold Schaitberger told the Hill Wednesday that administration officials had called "several leaders, particularly those directly involved in development of the resolution" prior to the vote in the hopes of soothing tensions.

"My understanding is that they would have preferred that no resolution be brought to the floor," Schaitberger said.

The problem for most unions with Obamacare is that the law does not extend its subsidies to multi-employer health insurance plans, while penalizing the plans in other ways. Most unions provide these for their members, and many are worried that employers will limit coverage or pull out altogether.

Labor leaders have lobbied the administration hard on the issue but the White House has thus far refused their request for a fix. Administration officials are leery of doing that because extending subsidies to multi-employer plans as the union leaders want would cause Obamacare's costs to soar at a time when they're already struggling to keep them under control.

One study found that extending the subsidies to the plans would cost taxpayers $187 billion over a decade.

Labor Secretary Tom Perez and While House Senior Adviser Valerie Jarrett both spoke at the convention, but neither promised anything beyond further talks with the administration on the subject.

"I know this president. He is here is for you. We may not agree on everything, but we always talk it through. We always resolve it," Perez said in his speech Tuesday.