WASHINGTON (AFP) - President Barack Obama on Thursday hailed the Supreme Court's decision to uphold his legacy-gilding health care law, casting it as a win for ordinary Americans.

"Today is a victory for hard-working Americans all across this country," Obama said in the White House Rose Garden, eschewing overt political gloating despite a victory that cements his signature domestic policy achievement.

Obama's Republican foes have tried repeatedly to overturn the law, which expanded insurance coverage to millions more Americans.

The Supreme Court decision was the most serious challenge to those reforms among 50 votes in Congress and a plethora of court filings.

In this instance, the high court's nine justices could have gutted subsidies essential to the programme.

"This is not about the Affordable Care Act as legislation or Obamacare as a political football. This is health care in America," Obama said.

"The Affordable Care Act is here to stay."

Slamming "misinformation campaigns" and "doomsday predictions," Obama quickly said he was ready to work with Republicans on further reforms.

"My greatest hope is that rather than keep refighting battles that have been settled again and again and again, I can work with Republicans and Democrats to move forward."

But in a sign of how central Obama believes the law is to his presidential legacy, he described it as on par with the passage of health care coverage for the oldest and very poorest Americans during Lyndon B. Johnson's 1960s "War on Poverty."

"This generation of Americans chose to finish the job, to turn the page on a past when our citizens could be denied coverage just for being sick," he said.

Obamacare prevented insurers from barring people from coverage who had pre-existing medical conditions.