 Mr Obama said there would be a place for Mrs Clinton in his administration |
Barack Obama has declared himself "the Democratic nominee for President of the United States".
The claim came on the last day of primary season, as projections showed he had earned enough delegates to clinch the nomination.
Of the two states that voted, Montana was won by Mr Obama, while in South Dakota, Mr Obama's rival Hillary Clinton was victorious.
In a speech to supporters, Mrs Clinton refused to concede the election.
Mr Obama's speech was delivered in St Paul, Minnesota, where Republicans are set to hold their presidential nominating convention.
In the speech, he stressed that Mrs Clinton would play a part in his administration.
Open mind
Speaking in New York, Mrs Clinton congratulated Mr Obama and his supporters "for all that they have accomplished".
Hillary Clinton: 'I will be making no decisions tonight'
But she said she was making "no decisions tonight" about her continued presence in the race.
Earlier, she told congressional backers that she was "open" to the idea of being Mr Obama's vice-presidential running-mate.
Mr Obama was only a few delegates short of the 2,118 needed ahead of the polls closing in South Dakota and Montana.
And although he failed to win in South Dakota, he had managed to pick up enough endorsements during the day from the remaining uncommitted "super-delegates" - party officials with a free choice over who to support - to pass the winning post as soon as polls closed in the state.
His projected victory in Montana added even more delegates to his tally.
Before the voting was complete, Republican presumptive nominee John McCain delivered a speech to supporters in Louisiana, in which he declared that "the primary season is over, and the general election campaign has begun".
He attacked Mr Obama for being "the wrong change", and defended himself against the Obama campaign's criticism that he will continue President Bush's policies, saying he had "not seen eye to eye" with the president on many issues.
