WASHINGTON — Nearly 9 million Americans have signed up for health coverage in 2018 through the federal HealthCare.gov website this year, according to an initial report from the Trump administration of the six-week enrollment period that ended last week.

The tally, though incomplete, suggests that enrollment on the HealthCare.gov insurance marketplace created by the Affordable Care Act will nearly equal the 2017 total despite uncertainty in the markets, a shorter enrollment period and efforts by the administration and GOP to roll back the law.

With sign-ups continuing in all or parts of 17 states, including the nation’s largest, total enrollment may ultimately surpass the 2017 tally.

The enrollment period on HealthCare.gov was half as long this fall as in previous years, and the Trump administration slashed funds for advertising and outreach. The president also often publicly referred to Obamacare as “dead” or “over.”

“Obamacare is finished. It’s dead. It’s gone,” Trump declared on the eve of the open enrollment period, which began Nov. 1.

In 2017, more than 12 million people signed up for Affordable Care Act marketplace plans, including about 9.2 million through HealthCare.gov.

Through last Friday, more than 8.8 million people had signed up for 2018 coverage through HealthCare.gov, according to the administration. That includes nearly 2.4 million new customers and 6.4 million returning enrollees, many of whom were automatically re-enrolled.

“It’s incredible how many people signed up for coverage this year with record-setting demand for affordable health coverage,” said Lori Lodes, a spokeswoman for Protect Our Care, a non-governmental advocacy group that stepped in to publicize the marketplaces when the Trump administration slashed outreach efforts.

“The demand for affordable coverage speaks volumes — proving, yet again, the staying power of the marketplaces,” Lodes said.

Seema Verma, a Trump appointee who heads the federal Centers for Medicare and Medicaid Services andwho had been silent about the enrollment period, announced the tally in a Twitter post Thursday.

“Great job to the @CMSGov team for the work you did to make this the smoothest experience for consumers to date. We take pride in providing great customer service,” Verma tweeted.

The marketplaces — a centerpiece of the law commonly called Obamacare — have primarily served low- and moderate-income Americans who don’t get health benefits through an employer or a government program such as Medicare or Medicaid.

They have been buffeted all year by uncertainty over their future, with insurers in some areas raising rates steeply or exiting markets altogether.

That has been particularly tough for consumers who make too much to qualify for federal insurance subsidies through the health care law.

The law offers subsidies to Americans making between 100 percent and 400 percent of the federal poverty line, or between $12,060 and $48,240 a year.

Many insurers also concentrated the rate hikes in certain plans. Because of the complex way the law calculates subsidies, that means many consumers will pay less for coverage in 2018.

Nine of the 17 states where people can still sign up for 2018 coverage — including California, Maryland, Connecticut and New York — operate their own marketplaces and are holding longer enrollment periods. California’s goes until the end of January. Maryland’s is scheduled to close Friday.

Residents of all or part of eight more states that rely on the federal HealthCare.gov site have until Dec. 31 because the states were affected by extreme weather such as hurricanes this fall.

Among the states affected were Florida, Georgia and Texas, all of which have had substantial enrollment in past years.