BOSTON - US President Barack Obama eulogized Senator Edward Kennedy Saturday as a "champion" of the poor and dispossessed, unbroken by tragedies which tore without mercy at his political clan.

In a poignant and affectionate address at Kennedy's funeral, Obama dubbed Kennedy, who died Tuesday aged 77, a "Happy Warrior" who triumphed over "more pain and tragedy than most of us will ever know."

The veteran senator from Massachusetts, the last of a trio of brothers who defined a heady, tragic political age, was a "champion for those who had none; the soul of the Democratic Party; and the lion of the US Senate," Obama said.

The president was making his debut as the effective leader of national mourning -- one of the ceremonial duties of the US president -- since capturing the White House, after a hefty assist from his mentor Kennedy.

He spoke to mourners in a spectacular Roman Catholic basilica in Boston, before Kennedy's widow Vicki, members of the extended Kennedy dynasty, and former presidents Jimmy Carter, Bill Clinton and George W. Bush.

Describing the man who charged him with keeping the Kennedy flame of charismatic liberal politics alive, Obama said his friend had rare resilience and carved purpose from the trials of his family and his own troubled personal life.

"This spirit of resilience and good humor would see Ted Kennedy through more pain and tragedy than most of us will ever know," Obama said, his words echoing through the cavernous and ornate Our Lady of Perpetual Help church.

"He lost two siblings by the age of sixteen. He saw two more taken violently from the country that loved them," Obama said, referring to the assassinations of Kennedy's brother, president John Kennedy and presidential candidate Robert Kennedy.

Obama also dwelt on the death of Kennedy's sister, Eunice, a few weeks ago, the moment when Kennedy cheated death in a plane crash and noted that as the surviving patriarch of the clan, Kennedy "watched two children struggle with cancer, buried three nephews, and experienced personal failings and setbacks in the most public way possible."

"It is a string of events that would have broken a lesser man... but that was not Ted Kennedy," Obama said, as some mourners daubed their eyes and others sniffed with emotion during an address that won a standing ovation.

Obama, who won Kennedy's priceless political endorsement during the most bitter days of his Democratic primary showdown with Hillary Clinton last year, also praised Kennedy's personal connection with those who knew him.

"Those of us who loved him, and ache with his passing, know Ted Kennedy by the other titles he held: Father. Brother. Husband. Uncle Teddy, or as he was often known to his younger nieces and nephews, "The Grand Fromage," or "The Big Cheese."

"Indeed, Ted was the "Happy Warrior."

At the climax of his address, Obama borrowed Kennedy's own words -- recalling his stemwinding Democratic convention address in 1980 when he roared a rallying call for liberal politics "the dream will never die" and his moving cancer-stricken reprise at the party convention last year when he promised "the dream lives on."

"Ted Kennedy has gone home now, guided by his faith and by the light of those he has loved and lost.

"At last he is with them once more, leaving those of us who grieve his passing with the memories he gave, the good he did, the dream he kept alive."

Obama painted "the image of a man on a boat; white mane tousled; smiling broadly as he sails into the wind, ready for what storms may come, carrying on toward some new and wondrous place just beyond the horizon."