KEY POINTS:
Barack Obama has started his run for the White House with a big obstacle cleared after Hillary Clinton rejected efforts by supporters urging the Democratic presidential nominee to choose her as his running mate.
"I will be speaking on Saturday about how together we can rally the party behind Senator Obama," Clinton told supporters in an email. "The stakes are too high and the task before us too important to do otherwise."
She is not lobbying for a spot on the ticket with Obama, communication director Howard Wolfson said.
"She is not seeking the vice presidency, and no one speaks for her but her," Wolfson said. "The choice here is Senator Obama's and his alone."
Aboard his plane between events, Obama said his search for a running mate will be secret. He called it the most important decision he will make for the duration of his campaign. Obama said he would not be rushed into a decision on choosing a vice president.
"I intend to do it right and I am not going to do it in the press," he said.
"The next time you hear from me about the vice presidential selection process will be when I have selected a vice president."
Obama has chosen a three-person team, including Caroline Kennedy, daughter of late President John F. Kennedy, to vet potential vice president candidates.
Clinton has told lawmakers privately that she would be interested in the vice presidential nomination, but her immediate task is bringing her presidential bid to a close.
If Obama made Clinton his running mate, it might help him tap into her core supporters, who have so far eluded him, including masses of blue-collar voters in swing states, Hispanics and older voters, especially women.
But, some of Clinton's closest supporters _ the nearly two dozen Democrats in the House of Representatives from her home state of New York - switched their allegiances to Obama.
The public announcement from the 23 in New York followed two days of private phone calls weighing her options. Another of Clinton's most prominent supporters, Ohio Gov. Ted Strickland, also announced his "wholehearted and enthusiastic support" for Obama on Thursday.
Clinton's move to formally declare that she is backing the Illinois senator came after Democratic congressional colleagues made clear they had no stomach for a protracted intra-party battle.
Now that Obama has secured the 2118 delegates necessary to clinch the nomination, Clinton had little choice but to end her quest, and sooner rather than later.
Obama's general-election battle against Republican John McCain, a veteran senator who effectively clinched the Republican nomination in March, is likely to focus on Iraq and McCain's relationship with the unpopular President George W. Bush.
The Illinois senator hit the ground running on the general election campaign trail against McCain in Virginia.
The state has long voted for Republican presidential candidates, but Democrats believe they can swing it into their camp for the general election after several years of inroads fuelled by the population swelling in the more liberal northern area of the state.
At a stop in Bristol, he criticised McCain, primarily over health care, and sought anew to link his Republican rival to Bush.
"Now, I respect John McCain, and I honour his service to this country. My differences with him are not personal; they're about the policies he's proposed on this campaign - policies that are no different than the ones that have failed us for the last eight years," Obama said.
Obama argued that health care premiums have risen faster than wages since Bush took office, and that millions more Americans are uninsured "yet John McCain actually wants to double down on the failed policies that have done so little to help ordinary Americans".
On his campaign plane, Obama praised Clinton for inspiring millions of voters and said she had opened the doors for his two young daughters to imagine being president one day.
"We're going to speak to them but also listen to them and get advice," he said of Clinton's campaign team.
Obama told reporters he appreciated the statement from Clinton's aide deferring to him on the running mate choice.
The Illinois senator noted Clinton had been involved in the selection process before when her husband, former President Bill Clinton, chose Al Gore as his running mate in 1992.
"We are going to be equally deliberative in how we move forward," Obama said as he travelled in Virginia, which is expected to be a battleground state in the campaign for the November general election.
Despite Obama's secrecy around his vice presidential deliberations, he's been sharing the media spotlight with someone cited frequently by pundits as a potential running mate: Virginia senator Jim Webb.
Webb, who had remained neutral as Obama and Clinton battled for the nomination, gave the Illinois senator an emphatic endorsement as he introduced him at a rally of 10,000 people in northern Virginia.
He referred to the ups and downs Obama faced in the long fight to secure the nomination. In the final few months of the race, Obama was battling daily attacks from both Clinton and McCain.
"I'm honoured to stand alongside this man, a man of great intellect who over the past 16 months has impressed all of us as he stood up to sometimes withering attacks with measured responses, unshakable composure," Webb said.
The decorated Marine veteran of the Vietnam War said Obama "has given all of us confidence in the steadiness that we want to see in a commander in chief."
Obama used his Virginia speech to look ahead to the November race against McCain.
He said he hoped they could have a respectful debate about policy issues and keep the campaign from getting bogged down by "name-calling" and "scandal-mongering".
The Illinois senator told McCain of that wish when the presumptive Republican nominee called Obama to congratulate him on Wednesday.
"I said that I was looking forward to a civil, substantive debate on the issues. And he agreed," Obama said, adding they discussed McCain's idea of appearing jointly at town-hall style forums.
Obama's campaign has said it is open to such formats and the two camps are exchanging views on options.
But Obama did not hold back from attacking McCain. At an event in southwestern Virginia earlier in the day, Obama likened his Republican rival's health care proposals to those of the unpopular President George W Bush. He said McCain's ideas amounted to "Bush light".
McCain's campaign hit back, deriding Obama's attempts to cast himself as someone who could rise above party divisions.
"Barack Obama has no record of bipartisan success," said McCain spokesman Tucker Bounds, adding Obama had voted "in lock-step with his party on issues from tax relief to funding of the Iraq war".
- AGENCIES
