WASHINGTON — The Trump administration on Thursday announced proposed rule changes that would lead to a modest premium increase next year under the Affordable Care Act. The roughly 1 percent increase could feed into the Democratic argument that the Trump administration is trying to “sabotage” coverage for millions.

The latest details were in a 300-page proposed regulation released Thursday by the Centers for Medicare and Medicaid Services.

The agency said the reason for the change is to more accurately calculate premium subsidies under the law. About 10 million people who don’t get health insurance on the job purchase individual policies under the ACA, and roughly 9 in 10 receive taxpayer-provided assistance with their premiums.

Premiums under the health law were basically stable this year after several sharp annual hikes. President Donald Trump, who once predicted “Obamacare” would “implode” or “explode,” took credit for calm insurance markets. He said it reflects his administration’s management skills.

The proposed regulation is open for public comment for 30 days.