Reporting from WASHINGTON—
The Obama administration has quietly adjusted key provisions of its signature healthcare law to potentially make billions of additional taxpayer dollars available to the insurance industry if companies providing coverage through the Affordable Care Act lose money.

The move was buried in hundreds of pages of new regulations issued late last week. It comes as part of an intensive administration effort to hold down premium increases for next year, a top priority for the White House as the rates will be announced ahead of this fall’s congressional elections.

Administration officials for months have denied charges by opponents that they plan a “bailout” for insurance companies providing coverage under the healthcare law.

They continue to argue that most insurers shouldn’t need to substantially increase premiums because safeguards in the healthcare law will protect them over the next several years.

But the change in regulations essentially provides insurers with…