Updated

Thirty-one Republican senators are urging the White House to reject union "demands" that ObamaCare subsidies be extended to some workers that already have coverage through their jobs, saying this is blatantly prohibited under the law.

The senators fired off a letter to President Obama Thursday following a newspaper report that unions -- worried that the law's other requirements would drive up the price of health care plans -- want lower-paid workers to have access to federal subsidies.

According to The Wall Street Journal, the Obama administration dismissed the idea early on of giving aid to workers in union-sponsored policies. But a Treasury official, in the same article, said the issue is "the subject of pending regulations."

This raised a red flag for senators.

"We respectfully, but strongly, disagree," the senators wrote. "The statement made by Treasury simply ignores the letter of the law."

More On This...

    A number of provisions in the health care law threaten to raise the cost of coverage, including the elimination of caps on benefits. The unions, echoing statements by employers across the country, voiced concern that the increase in up-front coverage costs could lead unionized employers to drop health coverage.

    But the senators said workers with an employer-based plan simply cannot, under the law, receive subsidies intended for those who don't get insurance through their jobs.

    "The Patient Protection and Affordable Care Act (PPACA) is not ambiguous, in fact it is explicit, on this point," the lawmakers wrote. "Any consideration of expanding access to subsidies therefore is not subject to regulation, but a change in the law."

    They cited one Congressional Research Service report that said employer-sponsored coverage would "generally" make an employee "ineligible to receive a premium subsidy."

    The subsidies, along with most major provisions of the health care law, are set to go into effect next year.

    According to the Journal, 20 million people are covered in plans run by unions and employers.

    Those signing the letter to Obama included Senate Republican Leader Mitch McConnell, R-Ky., Sen. Orrin Hatch, R-Utah., and Sen. John Barrasso, R-Wyo.

    "Concerns about rising premiums are driven by policies in (the health care law)," they wrote. "Rather than considering a diversion of subsidies not remotely contemplated in the statute, perhaps the concerns being raised by union plans should be cause to revisit the taxes, fees and other policies that drive premium increases."