Kennedy 'never forgot the sheer terror and helplessness that any parent feels when a child is badly sick. And he was able to imagine what it must be like for those without insurance, what it would be like to have to say to a wife or a child or an aging parent, there is something that could make you better, but I just can't afford it', Obama said.

About 46 million people in the US are estimated to be without health insurance.

Kennedy represented Massachusetts in the Senate for 47 years. He was known as the 'last lion' of the chamber, carrying the torch for left-leaning Democrats but also harbouring an ability to reach compromises with Republicans.

Kennedy first launched a campaign for health reform in 1969 and helped extend coverage to children and the disabled. But the last surviving brother of the famed Kennedy dynasty did not live to see his cause of comprehensive reform come to fruition.

'I feel confident in these closing days that while I will not be there when it happens, you will be the president who at long last signs into law the health care reform that is the great unfinished business of our society,' Kennedy wrote to Obama.