The number of people who have signed up and paid for President Barack Obama's signature healthcare plan is higher than estimated, say officials.
Figures released on Thursday showed 7.3 million people had paid their monthly premium for the marketplace scheme.
Original independent forecasts had predicted six million users, and there was a botched launch last year.
But the figure was down from the eight million who initially signed up when the scheme opened.
"We are encouraged by the number of consumers who paid their premiums," healthcare official Marilyn Tavenner said.
The administration released the data during a heated committee hearing in the US House of Representatives.
Republican lawmakers criticised Ms Tavenner about security issues around the online site for a federal Obamacare marketplace in 36 states.
The Patient Protection and Affordable Care Act is the largest overhaul of the US healthcare system since the 1960s.
It aims to extend health insurance coverage to some of the estimated 15% of the US population who lack it.
To achieve this, the law requires all Americans to have health insurance, but offers subsidies to make coverage more affordable and aims to reduce the cost of insurance by bringing younger, healthier people into the health insurance system.
It also requires businesses with more than 50 full-time employees to offer health coverage, although this provision was delayed until 2015 to allow more time for compliance.
The law creates marketplaces - with websites akin to online travel and shopping sites - where individuals can compare prices as they shop for coverage.
In addition, the law bans insurance companies from denying health coverage to people with pre-existing health conditions, allows young people to remain on their parents' plans until age 26, and expands eligibility for the government-run Medicaid health programme for the poor.
The law aims eventually to slow the growth of US healthcare spending, which is the highest in the world.
Republicans say the law imposes too many costs on business, with many describing it as a "job killer".
They have also decried it as an unwarranted intrusion into the affairs of private businesses and individuals.