Barack Obama met privately with Hillary Rodham Clinton, a likely vice presidential candidate, as the Democratic nominee-in-waiting sought to unite his fractured party against Republican John McCain in November.

One of her top supporters, fellow New York senator Charles Schumer, said Friday that Clinton would accept the number 2 spot.

''She has said if Senator Obama should want her to be vice president and thinks it would be best for the ticket, she will serve, she will accept that. But on the other hand, if he chooses someone else, she will work just as hard for the party in November,'' Schumer told ABC's Good Morning America.

Clinton and Obama met in Washington Thursday night, going to great lengths to keep the meeting secret from the media beforehand. Schumer said the meeting was not about the vice presidency.

Robert Gibbs, an Obama spokesman, said the meeting was to talk about uniting the Democratic Party.

''Senator Obama and Senator Clinton did have occasion to meet this evening,'' Gibbs said late Thursday. ''It's the end of the primary process. They wanted to talk about bringing these campaigns together in unity.''

Clinton has organized an event for Saturday in Washington, where she has told supporters she will formally end her campaign and back Obama for president.

Gibbs would not say where the former rivals met, except that it was not at Clinton's home in Washington, as had been widely reported. CNN reported Friday that the meeting was at California senator Dianne Feinstein's home.

Reporters traveling with Obama sensed something might be happening between the pair when they arrived at his campaign plane after an event in northern Virginia and he was not aboard.

Asked at the time about the Illinois senator's whereabouts, Gibbs smiled and declined to comment.

Clinton spokesman Howard Wolfson said the former first lady isn't waging a campaign for number 2.

''She is not seeking the vice presidency, and no one speaks for her but her,'' Wolfson said Thursday. ''The choice here is Senator Obama's and his alone.''

Obama on Tuesday night achieved the 2,118-delegate threshold he needed to secure the Democratic nomination. (AP)