The former first lady praised her rival warmly in an appearance before supporters in New York in which she neither acknowledged Obama's victory nor offered a concession of any sort.

Instead, she said she was committed to a united party and said she would spend the next few days determining "how to move forward with the best interests of our country and our party guiding my way."

Only 31 delegates were at stake in the two states on the night's ballot, the final few among the thousands that once drew Obama, Clinton and six other Democratic candidates into the campaign to replace Bush and become the nation's 44th president.

Obama sealed his nomination, according to The Associated Press tally, based on primary elections, state Democratic caucuses and support from party "superdelegates." It takes 2,118 delegates to clinch the nomination at the convention in Denver this summer, and Obama had 2,154 by the AP count.

Obama, a first-term senator who was virtually unknown on the national stage four years ago, defeated Clinton, the former first lady and one-time campaign front-runner, in a 17-month marathon for the Democratic nomination.

His victory had been widely assumed for weeks. But Clinton's declaration of interest in becoming his ticketmate was wholly unexpected.

She expressed it in a conference call with her state's congressional delegation after Rep. Nydia Velazquez predicted Obama would have great difficulty winning the support of Hispanics and other voting blocs unless the former first lady was on the ticket.

"I am open to it" if it would help the party's prospects in November, Clinton replied, according to participants who spoke on condition of anonymity because the call was private.

Clinton's comments raised anew the prospect of what many Democrats have called a "Dream Ticket" that would put a black man and a woman on the same ballot, but Obama's aides were noncommittal. "We're not in the presidential phase here. We're going to close out the nominating fight and then we'll consider that," David Axelrod, Obama's top strategist, told reporters aboard the candidate's plane en route to Minnesota.

McCain's criticism of Obama referred to a vote last year in which the Illinois senator came out against legislation paying for the Iraq war because it did not include a timetable for withdrawing troops. At the time, Obama said the funding would give President Bush "a blank check to continue down this same, disastrous path."

Obama previously had opposed a deadline for troop withdrawal, but shifted position under pressure from the Democratic Party's liberal wing as he maneuvered for support in advance of the primaries.