'Obamacare' grace period after 31 March deadline
The Obama administration is extending this month's deadline for people who were unable to get medical insurance in time under the healthcare law.
Applicants will have to demonstrate that special reasons prevented them enrolling by 31 March, such as glitches on the federal health coverage website.
Health officials did not specify how long the grace period would last.
The White House is racing to meet a goal of getting six million people signed up through new online markets.
'Surge in demand'
Five million people have already enrolled for premiums under the law, which is known as Obamacare.
The healthcare.gov website - which has been overhauled since its disastrous launch last October - saw more than one million visitors on Monday.
"We are experiencing a surge in demand and are making sure that we will be ready to help consumers who may be in line by the deadline to complete enrolment, either online or over the phone," Health and Human Services spokesman Aaron Albright said on Tuesday.
The decision will affect the 36 states where health insurance sign-ups take place via the federal government website.
Under the Affordable Care Act, it is now compulsory for people to have health cover - either provided for by their employer or by buying a private health plan.
Those who cannot afford it may qualify for benefits, but those without any insurance will face tax penalties.
Opinion polls show that the majority of Americans do not support the 2010 law, which represents the biggest overhaul of the multi-trillion dollar US healthcare system since the 1960s.
Conservatives are expected to try to tap into this discontent during November's midterm elections, which will determine the shape of Congress for Mr Obama's last two years in office.