FILE PHOTO: A sign on an insurance store advertises Obamacare in San Ysidro, San Diego, California, U.S., October 26, 2017. REUTERS/Mike Blake

WASHINGTON (Reuters) - The Trump administration took additional steps to weaken Obamacare on Monday, allowing U.S. states to relax the rules on what insurers must cover and giving states more power to regulate their individual insurance markets.

The Centers for Medicare and Medicaid Services issued a final rule that allows states to select essential health benefits that must be covered by individual insurance plans sold under former President Barack Obama’s healthcare law. The 2010 Affordable Care Act requires coverage of 10 benefits, including maternity and newborn care and prescription drugs. Under the new rule, states can select from a much larger list which benefits insurers must cover.

That could lead to less generous coverage in some states, according to Avalere Health, a research and consulting firm.

President Donald Trump’s administration has used its regulatory power to undermine Obamacare after the Republican-controlled Congress last year failed to repeal and replace the law. About 20 million people have received health insurance coverage through the program.

The new CMS rule also allows states the possibility of modifying the medical loss ratio (MLR) formula, the amount an insurer spends on medical claims compared with income from premiums that is also a key performance metric. A state can request “reasonable adjustments” to the medical loss ratio standard if it shows that it could help stabilize its individual market.

Insurers could also have an easier time raising their rates under the new rule. Obamacare mandated that premium rate increases of 10 percent or more in the individual market be scrutinized by state regulators to ensure that they are necessary and reasonable. The new CMS rule raises that threshold to 15 percent.