WASHINGTON — For a few puzzling moments Thursday, US President Barack Obama believed inaccurate media reports that his proudest political achievement -- health care reform -- had been shot down.

Obama was standing in the outer Oval Office watching a split screen of four cable news channels when reports flashed by that the historic reform had been invalidated by the Supreme Court, senior officials said.

Two stations, CNN and Fox News, at first erroneously said the Court had struck down the centerpiece of the law, a mandate requiring all Americans to buy health insurance.

But one senior official, speaking on condition of anonymity, said a quizzical Obama was quickly joined by his chief law counsel Kathy Ruemmler, who gave him good news on the law by giving him two thumbs up.

Ruemmler was relying on a lawyer in the Supreme Court chamber for news of the judgment, and later analysed the ruling herself, confirming the news the White House had been hoping to hear.

Obama then hugged Ruemmler and placed his first call to the US Solicitor General Donald Verrilli, who was widely panned over his oral arguments before the court but was eventually vindicated by its decision.

Such is the secrecy of the Supreme Court, other top officials had no advance warning on the fateful judgment and had to rely on television stations and the popular SCOTUS blog which decodes the legalese of Court decisions.