Washington  - US President George W Bush on Tuesday took his first real foray into 2008 election politics, joining the presumptive Republican nominee John McCain for a fundraising event in Arizona.

Bush and McCain appeared at a closed-door event at a private home in Phoenix, one of three fundraisers the former rivals plan to attend in the coming days. Bush will also be stumping for congressional candidates.

McCain, who lost a bitter 2000 primary campaign to the current president, welcomed Bush's endorsement at a White House gathering in March - their only significant joint appearance to date.

But the long-time senator from Arizona has also sought to distance himself from the deeply unpopular administration, sharply criticizing Bush on issues ranging from global warming and torture, to dealing with US allies and the international community.

The White House said the criticism is to be expected, but that Bush was available to campaign throughout the country for McCain as well as other Republican candidates.

"Every election is about change - go back through history and every single one is about how things are going to look in the future," said White House spokesman Dana Perino. "That's what Senator McCain has set out to do, which is to chart his own course."

Democrats have regularly tied McCain to Bush's unpopular policies in Iraq and on the economy, arguing a vote for McCain in November amounts to a vote for a third Bush term.

McCain strongly supports the war in Iraq and approves of extending tax cuts that Democrats charge only help the country's wealthy.

Barack Obama, the Democrats' own likely presidential candidate, suggested that Tuesday's private fundraiser was a sign of McCain's own ambivalence toward the commander-in-chief, whose job approval ratings have long hovered around 30 per cent.

"Senator McCain doesn't want to be seen hand-in-hand with the president whose failed policies he promises to continue for another four years," Obama said at a campaign event in Las Vegas, Nevada.

McCain and Bush were expected to appear together briefly after Tuesday's event, at an airport tarmac in Phoenix, the White House said.

Bush has long been recognized as a prolific fundraiser, breaking records in his 2000 and 2004 re-election campaign.

Those records have since been broken by Obama and his rival Hillary Clinton, while McCain has this year struggled to match the Democrats' fundraising prowess. (dpa)