The Republican Party may have renewed efforts to repeal Obamacare, but millions of people keep buying into the plan.

A couple enrolls in Obamacare with an insurance agent in Atlanta. Getty Images

Sign-ups for Obamacare insurance have topped 11.3 million nationally, officials revealed Thursday.

The report was the first release of cumulative enrollment to date for 2016 plans from both the federal Obamacare exchange HealthCare.gov — which serves 38 states — and from the 13 health insurance marketplaces run by individual states and the District of Columbia. The national tally puts the Obama administration well on track to meet its stated goal of 10 million paying customers by the end of 2016, a target that takes into account the way that enrollment tends to drift lower over the course of a calendar year.

About 8.6 million people signed up for plans on HealthCare.gov since Nov. 1, and another 2.7 million signed up on the state-based exchanges, officials said. Nearly 4 million people under age 35 nationally signed up for Obamacare plans. That number is important: The 18-to-34-year-old demographic is closely watched, because younger customers tend to spend more into the health plans than they cost in benefits. Almost 3 million of the sign-ups came from those young adults. "We're encouraged that marketplace consumers are increasingly young, engaged and shopping for the best plan," said Health and Human Services Secretary Sylvia Burwell. "We have more work to do before the next deadlines, and our focus continues to be the consumer experience and educating consumers about available financial assistance and their choices."

The report comes roughly three weeks before the Jan. 31 close of open enrollment, and as the Obama administration and health-care advocates continue to try to lure people who still don't have health insurance. Officials noted that people who want coverage effective Feb. 1 must sign up by Jan. 15. HealthCare.gov on Thursday morning sent out an alert to would-be customers, warning that they face a tax penalty of $695 or more if they fail to sign up for insurance this year. The enrollment report also came hours after Gallup revealed that the percentage of Americans without health insurance has increased for the first time since Obamacare began taking full effect. In the fourth quarter of 2015, 11.9 percent of U.S. adults did not have health coverage, up from 11.6 percent in the third quarter of the year, the Gallup-Healthways Well-Being Index found.

However, the uninsured rate is still 5.2 percentage points lower than it was in the last quarter of 2013, which is when Obamacare plans first went on sale. And Gallup, in a report on the survey, noted that the uninsured rate in the first quarter of 2016 "is more likely to show a decline," given the ongoing open-enrollment period. There is widespread consensus that the large decrease in the number of people without health insurance in the U.S. over the past two years has stemmed from the Affordable Care Act, which requires most people to have some form of health coverage or face a fine. By the last half of 2015, more than 9 million paying customers were enrolled in private health insurance plans sold on government-run Obamacare exchanges. Another 13.5 million people had been added to the rolls of Medicaid — the government-run health coverage program for the poor — since late 2013.