WASHINGTON — Senator Clinton told colleagues today she would be consider joining Senator Obama as his running mate, and advisers said she was withholding a formal departure from the race partly to use her remaining leverage to press for a spot on the ticket.

On a conference call with other New York lawmakers, Mrs. Clinton, a New York senator, said she was willing to become Mr. Obama’s vice presidential nominee if it would help Democrats win the White House, according to a participant who spoke on condition of anonymity because this person was not authorized to speak for Mrs. Clinton.

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Mrs. Clinton’s remarks came in response to a question from Rep. Nydia Velazquez, a Democrat of New York, who said she believed the best way for Mr. Obama to win key voting blocs, including Hispanics, would be for him to choose Mrs. Clinton as his running mate.

“I am open to it,” Mrs. Clinton replied, if it would help the party’s prospects in November.

Mrs. Clinton also told colleagues the delegate math was not there for her to overtake Mrs. Obama, but that she wanted to take time to determine how to leave the race in a way that would best help Democrats.

“I deserve some time to get this right,” she said, even as the other lawmakers forcefully argued for her to press Mr. Obama to choose her as his running mate.

Aides to the Illinois senator said he and Mrs. Clinton had not spoken about the prospects of her joining the ticket.

Mr. Obama effectively sewed up the 2,118 delegates needed to win the nomination today, based on a tally of pledged delegates, superdelegates who have declared their preference, and another 18 superdelegates who have confirmed their intentions to The Associated Press. It also included five delegates Mr. Obama was guaranteed as long as he gained 15% of the vote at South Dakota and Montana later in the day.

Word of Mrs. Clinton’s vice presidential musings came as she prepared to deliver a televised address to supporters on the final night of the epic primary season. She was working out final details of the speech at her Chappaqua, N.Y., home with her husband, President Clinton, their daughter, Chelsea, and close aides.

Earlier, on NBC’s “Today Show,” the Clinton campaign chairman, Terry McAuliffe, said that once Mr. Obama gets the majority of convention delegates, “I think Hillary Clinton will congratulate him and call him the nominee.”

Mrs. Clinton will pledge to continue to speak out on issues like health care. But for all intents and purposes, two senior officials said, her campaign is over.

Most campaign staff will be let go and will be paid through June 15, said the officials who spoke on condition of anonymity because they were not authorized to divulge her plans.

The advisers said Mrs. Clinton has made a strategic decision to not formally end her campaign, giving her leverage to negotiate with Mr. Obama on various matters including a possible vice presidential nomination for her. She also wants to press him on issues he should focus on in the fall, such as health care.

Universal health care, Mrs. Clinton’s signature issue as first lady in the 1990s, was a point of dispute between Mr. Obama and the New York senator during their epic nomination fight.

In a formal statement, the campaign made clear the limits of how far she would go in tonight’s speech. “Senator Clinton will not concede the nomination,” the statement said.

Clinton field hands who worked in key battlegrounds said they were told to stand down, without pay, and await instructions. Speaking not for attribution because they didn’t want to jeopardize their jobs searches, many said they were peddling resumes, returning to their hometowns, or seeking out former employers.

Clinton officials have said they would not contest the seating of Michigan delegates at the convention in Denver this August. The campaign was angry this past weekend when a Democratic National Committee panel awarded Mr. Obama delegates it thought Mrs. Clinton deserved.