The voice of the late senator Ted Kennedy echoed round the joint session of Congress Wednesday as President Barack Obama read a letter from Kennedy which was only to be delivered on his death.

Obama said he had received the letter in the past few days after Kennedy's death on August 27.

"He repeated the truth that health care is decisive for our future prosperity, but he also reminded me that it concerns more than material things," said Obama as Kennedy's widow Vicki, and his two sons, Patrick and Teddy Jr, looked on.

In the letter, Kennedy said the country faced a moral issue on "fundamental principles of social justice and the character of our country."

He said he hoped that Obama would be able to change the status quo in America; that a family's health would never again depend on their wealth.

The letter was dated May 12, and Kennedy had asked that it be delivered after his death.

He also paid tribute to Obama and his wife Michelle for their kindnesses during the difficult months toward the end.

"I wanted to write a few final words to you to express my gratitude for your repeated personal kindnesses to me – and one last time, to salute your leadership in giving our country back its future and its truth.

"On a personal level, you and Michelle reached out to Vicki, to our family and me in so many different ways. You helped to make these difficult months a happy time in my life.

"You also made it a time of hope for me and for our country."

"With deep respect and abiding affection,"