The Obama campaign announced that Winfrey will be joining the candidate's wife Michelle and Caroline Kennedy, daughter of slain president John F. Kennedy (president 1961-1963) at a Sunday rally in Los Angeles.

According to opinion polls, Ms Winfrey is one of the most admired women in the United States, second only to Obama's rival presidential hopeful, Hillary Clinton.

Obama's Los Angeles rally is being held just days before 'Super Tuesday', when voters in 24 states, including populous states like California, New York, and Illinois, will cast ballots for their respective party's nominees.

In December, the talk show megastar campaigned with Obama in Iowa, New Hampshire and South Carolina, attracting the largest crowds of any campaign and helping raise some three million dollars.

Ms Winfrey has a strong appeal to women voters - a group in which Clinton is especially popular - that crosses racial barriers.

Caroline Kennedy endorsed Obama one week ago, comparing the Illinois senator to her father in his ability to inspire voters.

Her uncle, Senator Edward Kennedy, endorsed Obama on Monday and has been campaigning for him in key states such as California, where opinion polls show that Clinton has a strong lead.

The Clinton campaign is quick to point out that their candidate is endorsed by Robert Kennedy junior, Kerry Kennedy and Kathleen Kennedy Townsend, all children of president Kennedy's younger brother Bobby, assassinated in 1968.

Separately, Obama on Saturday received the endorsement of Susan Eisenhower, granddaughter of 'Ike' Eisenhower, the World War II D-Day commander who was US president 1953-1961 and the man who preceded John Kennedy as president.

'I am convinced that Barack Obama is the one presidential candidate today who can encourage ordinary Americans to stand straight again; he is a man who can salve our national wounds and both inspire and pursue genuine bipartisan cooperation,' Eisenhower wrote in a Washington Post opinion piece.

'If the Democratic Party chooses Obama as its candidate, this lifelong Republican will work to get him elected and encourage him to seek strategic solutions to meet America's greatest challenges,' she wrote.

'To be successful, our president will need bipartisan help.' Eisenhower, a business consultant and author, is part of a small but growing group dubbed 'Obama-cans', Republicans who support Obama's candidacy.

Both Obama and Clinton campaigned in western states on Friday, especially focusing on vote-rich California.

On Friday, Obama received a glowing endorsement in The Los Angeles Times, the leading newspaper in the largest US city.

The newspaper said it chose him over Clinton because of his promise and his early opposition to the war in Iraq.

He was also endorsed by the powerful leftist Internet-based group MoveOn.org, which counts some 3.2 million members. -- AFP