Washington  - Edward Kennedy, who for decades championed health care reform in the US Senate until his death last month, has spoken out one last time on the issue that was closest to his heart.

In a speech Wednesday to a joint session of Congress, President Barack Obama revealed that Kennedy wrote him a final letter in May - after being informed that his brain cancer was terminal - and instructed it to be delivered only after his death.

In the letter, released by the White House, Kennedy calls comprehensive health reform "the great unfinished business of our society." He said the "prospect of victory" in Congress after so many years had helped keep him going in the final months of his life.

"What we face is above all a moral issue," wrote Kennedy, who died August 26 at age 77. "At stake are not just the details of policy but fundamental principles of social justice and the character of our country."

Obama read an excerpt of the letter during his speech to Congress, in which he called on legislators to end their bickering of the last few months and pass major health reforms by the end of the year.

He said that Kennedy's own passion for health reform was borne out of personal experience: He lost two children to cancer.

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 United States 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. (dpa)