WASHINGTON — The nation’s progress in getting more people covered by health insurance slowed significantly this year, the government confirmed Wednesday in a report that tempers a historic achievement of the Obama administration.

About 1.3 million fewer people were uninsured the first three months of this year, driving the uninsured rate to a new record low of 8.6 percent, according to the National Health Interview Survey, an ongoing project of the Centers for Disease Control and Prevention.

Still, that progress is a fraction of the earlier gains seen under President Barack Obama’s health care law. When the law’s big expansion got underway in 2014, the number of uninsured people went down by nearly 9 million.

The uninsured rate has been cut by nearly half under Obama’s law, but that hasn’t been enough to overcome political divisions. The survey estimated that 27.3 million people remained uninsured in the first three months of this year, about 21 million fewer than in 2010, when Obama signed the Affordable Care Act.

The law offers subsidized private insurance for people everywhere who don’t have access to job-based coverage, along with a Medicaid expansion geared to low-income adults in states that opt for it. Although a growing economy should also be contributing to coverage gains, experts say the law deserves most of the credit.

In another notable finding, the report said the share of working age people and dependents with high-deductible health insurance has increased and now stands at 4 out of 10. Such plans require patients to pay a sizable share of their medical bills before insurance kicks in. The survey defined that as at least $1,300 annually for self-only coverage, and $2,600 for a family.

The trend toward high-deductible plans started before Obama took office but advanced during his tenure as employers sought to limit their costs. In 2010, only about 25 percent of people under age 65 were in such plans. Policy experts credit rising deductibles for helping to restrain overall health care spending, but employees generally see that as a cost shift to them. Polls suggest the trend has undercut support for Obama’s health care overhaul.

The administration accentuated the survey’s positive finding that the uninsured rate hit a new low.

“Our country’s march toward improving access, quality and affordability in health care goes on, and today’s numbers show that the Affordable Care Act is continuing to drive historic progress,” Health and Human Services Secretary Sylvia Burwell said in a statement.

The slower progress registered in the CDC report echoed recent findings from a major private survey, the Gallup-Healthways Well-Being Index.

The government survey found 8.8 million fewer uninsured people in 2014. The following year, 2015, there was a reduction of 7.4 million. That compares with 1.3 million fewer uninsured people in the first three months of this year.

The numbers for 2014 and 2015 are for full calendar years. But the new figures for the first three months of 2016 are considered a reliable indicator for the rest of the year. That’s because the health care law’s open enrollment deadlines drive sign-ups early in the year.

The upcoming 2017 sign-up season looks tough, with sharp premium increases in many communities and a dwindling choice of insurers. Democratic presidential candidate Hillary Clinton has promised to help the health care law regain its momentum, while Republican Donald Trump would make good on the Republican vow to repeal “Obamacare” and replace it with a new program yet to be defined.

Some independent experts said the survey suggests that the health care law is approaching its limits, absent a change.

“The share of the population without health insurance is lower than it’s ever been…but further gains are getting harder and harder to achieve,” said Larry Levitt of the Kaiser Family Foundation. “The pace at which people are getting newly insured has noticeably slowed.”

“Low-income adults have come the farthest, but still have the farthest to go — nearly 25 percent of this population is uninsured,” said Katherine Hempstead of the Robert Wood Johnson Foundation. Covering more low-income adults is hindered because 19 states are still refusing the law’s Medicaid expansion.

“Multiple initiatives are needed to have a major impact on further reducing the uninsured population,” said Paul Hughes-Cromwick of the Altarum Center for Sustainable Health Spending, a research and consulting group.