President Biden announced Tuesday that the federal insurance marketplace will remain open for consumers to buy Affordable Care Act health plans through mid-August, doubling the length of an unprecedented extra enrollment period that launched last month.

Speaking at a cancer hospital and research institute at Ohio State University, Biden made the announcement as part of a recognition of the ACA’s 11th anniversary. The sprawling health-care law has helped more than 20 million Americans gain coverage through marketplace health plans and Medicaid, and it has altered many other aspects of the U.S. health-care system, even as it has remained a target of vehement Republican opposition.

“We have a duty not just to protect it but to make it better,” the president said before an audience that included oncologists and cancer researchers.

The lengthening of the special enrollment time reflects Biden’s determination to use the 2010 health-care law as a fulcrum to expand the number of Americans who have access to affordable insurance and, as a result, to care.

The extension of the deadline, from May 15 to Aug. 15, also reflects the administration’s hopes that an imminent increase in federal subsidies for ACA health plans will be a potent magnet to attract more Americans to this type of insurance.

The $1.9 trillion coronavirus relief plan that Biden signed into law this month contains the first increase since the law’s passage of the subsidies that already help nearly 9 in 10 people with ACA health plans pay for monthly premiums.

Starting April 1, subsidies will become larger for people who already qualify. Those tax credits would fully cover premiums for people with incomes of up to about $19,000 for an individual and nearly $40,000 for a family of four — that is, 150 percent of the federal poverty level.

And for the first time, the subsidies would reach many in the middle class, who have been among the groups finding ACA health plans unaffordable. The new law ends a rule that had set a ceiling on the premium subsidies, making them unavailable to consumers with incomes of more than about $51,000 for an individual and $106,000 for a family of four — 400 percent of the poverty line.

Starting in July, people who receive unemployment benefits — or have filed an unemployment claim any time this year — may qualify for additional reductions of their ACA insurance premium.

According to data released Tuesday by the Department of Health and Human Services, an estimated 11 million non-elderly Americans who are uninsured could qualify for discounted or premium-free coverage through the ACA marketplace.

The ACA health plans are intended for a niche of people who historically had a difficult time finding affordable health insurance before the health plans created under the law started in 2014: those who cannot get affordable health benefits through a job.

Last year, about 11 million people signed up for the marketplace coverage.

During the first two weeks after was reopened, more than 200,000 people signed up, according to federal figures.

The special enrollment is for consumers in three dozen states that rely on, the online enrollment system for buying ACA health plans. The other states run their own ACA marketplaces, and most of them have kept their enrollment open, particularly because the economic fallout from the coronavirus pandemic has cost millions of Americans their jobs — and the health benefits that came with them.

In the three dozen states, consumers can apply for ACA coverage for the first time. Or they can update the health plan choice they made during the most recent regular enrollment season late last year to claim a larger subsidy.

Biden has long been an ACA loyalist, He was vice president to President Barack Obama, for whom the ACA’s creation was a central domestic policy achievement of his eight years in the White House. In his remarks Tuesday, Biden recalled riding with Obama to the signing ceremony for the law.

At Ohio State, he urged consumers eligible for ACA health plans to take advantage of the unusual sign-up period, reminding them that they could go to or phone a federal call center.

“A few clicks and a short conversation,” Biden said, “and that’s all it takes to start seeing those benefits.”