Sen. Ted Kennedy made a surprise appearance at the Democratic National Convention in Denver Monday evening, sending the party faithful into a frenzy.

The ailing Kennedy recently underwent surgery and is suffering from brain cancer.

"It is so wonderful to be here and nothing was going to keep me away from this special gathering tonight," Kennedy said, his voice strong and clear.

Despite his bleak prognosis, he said he had this to say: "I pledge to you that I will be there next January on the floor of the United States Senate."

Kennedy spoke out strongly in support of Barack Obama, comparing the presidential hopeful to his brother, slain U.S. president John F. Kennedy.

"We are told that Barack Obama believes too much in an America of high principle and high endeavor," he said. "But when John Kennedy thought of going to the moon he didn't say, 'It's too far to get there, we shouldn't even try.'"

"Today an American flag still marks the surface of the moon."

A video tribute was planned for Kennedy but it wasn't clear he would be able to see it in person. He flew to Denver Sunday but doctors were said to be worried about his exposure to crowds because of his frail immune system.

Kennedy has been at every convention except two in the last 48 years.

Michelle Obama addresses nation

Michelle Obama, nicknamed "The Closer" for her convincing sales tactics, headlined the night and spoke about her husband's values and personal life.

"What struck me when I first met Barack was that even though he had this funny name, and even though he had grown up all the way across the continent in Hawaii, his family was so much like mine," she said.

"He was raised by grandparents who were working-class folks just like my parents, and by a single mother who struggled to pay the bills just like mine did. And like my family, they scrimped and saved so that he could have opportunities that they never had themselves.

"And Barack and I were raised with so many of the same values. Like you work hard for what you want in life, that your word is your bond and you do what you say you're going to do. And that you treat people with dignity and respect, even if you don't know them and even if you don't agree with them."

Aside from focusing on the couple's humble backgrounds -- aimed at countering Republican efforts to label Obama as "elitist" -- Michelle Obama also touched on her husband's work to improve the poor neighbourhoods of Chicago after he graduated from law school.

Michelle Obama, an Ivy league trained lawyer like her husband, has also worked for political and non-profit organizations, along with specializing in corporate law.

Her last job before stepping down to help her husband's campaign full-time was as a highly-paid executive for a Chicago Hospital.

Michelle Obama's speech was partly aimed at promoting herself as a potential first lady. She is seen as being closer to an outspoken Hillary Clinton rather than a traditionally quiet presidential spouse like Laura Bush.

In an interview aired Monday Obama told CNN Michelle Obama saw herself and her husband as "quintessential" Americans.

"Our stories are the quintessential American stories," she said. "I am here because of the opportunities that my father had, that my mother had. You know, we are who Americans were supposed to be."

Democrats support Obama

Congressman Jesse Jackson Jr. of Illinois spoke out in an impassioned speech Monday evening, describing Obama as a unifier and a leader "for the future."

"I know that while America may not be perfect our union can be always be perfected - I know what we can achieve when good people with strong conviction come together around a common purpose - and I know what a great leader can go to help us build common ground," Jackson said in a speech that hit on many of the same themes as Obama's famed 2004 convention speech.

"America we need such a leader, a leader who can heal the wounds of the last eight years, a leader who knows that unites us is greater than what divides us. America, we need Barack Obama."

Jackson made the speech while his father, the Rev. Jesse Jackson, sat in the audience at the Denver Pepsi Centre. The senior Jackson was noticeably left off the Democratic speaking after some controversial remarks he made about Obama earlier this summer.

"America realizes we can't four more years of the same ineffective governing," Democratic Party chairman Howard Dean said in the convention's call to order.

The convention kicked off just as party officials said that Sens. Hillary Clinton and Barack Obama have worked out a deal that will halt a potentially divisive presidential roll call at the Democratic National Convention in Denver.

Under the deal, the state by state delegate vote on Wednesday for the presidential nomination will allow some states the opportunity to vote for Clinton.

But after several states vote, Clinton will step in to ask all the remaining states to unanimously back Obama.

The move would serve to symbolically unify the party behind Obama, who is still struggling to win over some Clinton supporters after a hard-fought and close primary race.

But some Clinton supporters said the compromise wasn't enough and wanted more attention to be given to her primary victories.

The deal has not yet been officially announced by either Clinton or Obama's campaigns.

Obama needs to find a way to draw Clinton supporters back into the fold if the party hopes to win in the upcoming presidential election.

"When you look at those polls that say 30 per cent of Clinton supporters are now going to vote for John McCain -- he desperately needs to keep them on his side of the ledger," CTV's Washington Bureau Chief Tom Clark said from Denver Monday.

That support will be vital, Clark said, noting that the Clinton camp is still very strong and many feel they have been left out of the pre-election planning and even disrespected by the Obama crowd.

But in her first appearance at the convention, Clinton did her part to preach party unity.

At a breakfast meeting of New York Democrats, she attacked presumptive Republican presidential nominee John McCain -- who is running ads using Clinton's words against Obama.

"I'm Hillary Clinton, and I do not approve that message," she said.

She acknowledged the hard feelings left over from the primary race but encouraged her party to move past them.

"We were not all on the same side as Democrats, but we are now," she said. "We are united and we are together and we are determined."