Hillary Clinton formally ended her marathon bid to become the United States’ first woman president. She was addressing a tumultous farewell rally in Washington last night.
Clinton will use a party for campaign staff and supporters to suspend her 16-month campaign to become the Democratic Party's nominee.
She is expected to throw both her election machinery and support behind nominee Barack Obama. The news comes amid intense speculation about who Obama will choose to be his vice-presidential running mate.
Obama is not expected to attend Clinton's farewell event at the National Building Museum in Washington.
He did hold a private meeting with his defeated rival on Thursday.
Campaign aides said little about the meeting - which was ostensibly aimed at promoting party unity - but Mrs Clinton has distanced herself from reports that she was hoping to be on the November ticket with Obama.
Mrs Clinton kept a low-profile on Friday, while Obama made a surprise appearance at festivities in his hometown of Chicago to celebrate the city's place on the shortlist to host the 2016 Olympic Games.
The Illinois senator won delegates enough to secure the nomination after primaries in Montana and South Dakota on Tuesday.
Obama was a surprise guest at an Olympics rally in Chicago
A statement from Mrs Clinton's campaign on Thursday said: "While Senator Clinton has made clear throughout this process that she will do whatever she can to elect a Democrat to the White House, she is not seeking the vice-presidency."
It adds: "The choice here is Senator Obama's and his alone."
In her speech on Saturday, the former First Lady is expected to thank her supporters and urge Democrats to unite behind Obama in order to help him defeat the Republican presumptive nominee, John McCain, in November's election.
Obama, under pressure from Clinton backers to choose her as his running mate, has announced a team to help him make his selection and said he will not be rushed.
The BBC's Andy Gallacher in Washington says that if Obama were to choose her, this would be seen as a tactical move to win over the almost 18m people who cast their votes for Mrs Clinton.
McCain has challenged Obama to take part in debates in 10 town hall meetings before the Democratic convention in August.
The Obama team is said to be considering the invitation.
