"Together we have known success and seen setbacks ... but we have never lost our belief that we are all called to a better country and a newer world," he said. "I pledge to you that I will be there next January on the floor of the Senate."
His brief speech marked only the second time he has been seen in public since undergoing surgery for a brain tumor on June 2. His appearance came at his own insistence, a source close to the Kennedys said.
The 76-year-old senator compared Obama to his brother, the late president.
"We are told that Barack Obama believes too much in an America of high principle and bold endeavors," Ted said. "But when John F. Kennedy thought of going to the moon, he didn't say, 'It's too far to get there - we shouldn't even try.'
"Our people answered his call and rose to the challenge, and today an American flag still marks the surface of the moon."
He added: "This November, the torch will be passed again to a new generation of Americans. So, with Barack Obama and for you and for me, our country will be committed to his cause. The work begins anew. The hope rises again. And the dream lives on."