Barack Obama was coy about names in the frame for his pick of vice presidential nominee but was adamant that his choice would never be taken for a clone of Dick Cheney.

With speculation about his selection now rampant heading into next week's Democratic nominating convention in Denver, the White House contender said he wanted a running mate who has integrity and is unafraid to speak their mind.

"Here's what I won't do," the Illinois senator told a raucous crowd of 2600 people at an evening rally on Tuesday, launching an outspoken attack on President George W. Bush and his secretive and enormously influential deputy, Cheney.

"I won't hand over my energy policy to my vice president, without knowing necessarily what he's doing. I won't have my vice president engineering my foreign policy for me," Obama said.

'The buck will stop with me'

"The buck will stop with me, because I'll be the president."

Obama stayed clear of dropping any names, with an announcement expected any day now. But perhaps revealingly, he repeatedly used the pronoun "he," suggesting the pick will not be a woman such as Senator Hillary Clinton.

"My vice president also, by the way, will be a member of the executive branch, he won't be one of these fourth branches of the government where he thinks he's above the law," he said.

The New York Times reported late on Monday that Obama had narrowed down his search to Virginia Governor Tim Kaine, Indiana Senator Evan Bayh and Delaware Senator Joseph Biden, who is a foreign-policy veteran.

But Obama aides put up a wall of silence after promising to divulge the news to supporters first with a blitz of emails and text messages.

And according to MSNBC, Biden told reporters at his Delaware home: "I'm not the guy." Asked where he would be on Saturday as Obama speaks in Springfield, the senator pointed down to his driveway and said "here".

Obama did say: "I want somebody who has integrity, who's in politics for the right reasons.

"I want somebody who's independent, somebody who's able to tell me 'you know Mr president, I think you're wrong on this and here's why'."

Above all, he said, "I want somebody who is capable of being president, who I trust."

In a fighting mood

Despite suffering from a heavy cold, Obama was in fighting mood at the rally in Raleigh, North Carolina — one staunchly Republican state that his campaign is fighting hard for.

"I'm a big believer in winning. I don't intend to lose this election. John McCain doesn't know what he's up against right now," the Democrat said, after facing criticism for not taking a tougher line against his Republican rival.

The VP stakes intensified as aides announced that Obama will, on Saturday, return to the historic spot in Illinois where he launched his improbable White House quest to kick off a pre-convention tour of battleground states.

Perhaps accompanied by his vice presidential pick, Obama will speak at the Old State Capitol in Springfield, the hometown of venerated Civil War president Abraham Lincoln and the same site he began his bid way back in February 2007.

On Wednesday next week he will be crowned the party's standard-bearer to take on McCain in November's election, and will give his acceptance speech the next day before up to 80 000 supporters in a Denver sports stadium.

'Hyped by the media'

While the convention will proclaim party unity, disaffected supporters of Obama's defeated rival Clinton plan to put on a show of protest. But the new champion said talk of Democratic division was "hyped by the media."

"We had a vigorous campaign. Senator Clinton ran a historic campaign," he said, adamant the former first lady was now fully on board his shot at becoming America's first black president.

After a hot summer of charge and counter-charge on the economy and national security, the presidential race rests on a knife-edge ahead of the party conventions, with the Republicans gathering in early September.

A Los Angeles Time/Bloomberg survey had Obama on 45 percent and McCain on 43 percent — a statistical dead heat.

McCain, battling to carve an opening on the economy, meanwhile flew to a Gulf of Mexico oil rig 220 kilometres off New Orleans to demand expanded offshore drilling.

"Senator Obama opposes new drilling, he said it won't solve our problem and that it's 'not real' — he is wrong and the American people know it," the Arizona senator said.

"The nation is sending $700-billion every year overseas to (oil-exporting) countries that do not like us very much. When I am president that is going to stop," he said.

AFP