Barack Obama launched his strongest attack yet on his Republican rival John McCain as he accepted the Democratic Party's presidential nomination, US political analysts said yesterday.

In the most important speech of his career, Mr Obama told more than 80,000 people packed in an outdoor stadium that the American dream was alive and the nation can be better than it has been during the last eight years of President George W Bush.

"If John McCain wants to have a debate about who has the temperament, and judgment, to serve as the next commander-in-chief, that's a debate I'm ready to have," Mr Obama declared, referring to his rival's notorious temper and criticism of his own lack of experience.

The New York Times said he "went so far as to attack the presumed strength of Mr McCain's campaign, national security."

The Washington Post said the keynote address "was less lofty than his earlier rhetorical forays, more specific on the policies he would pursue as president and more scathing towards McCain".

And the Los Angeles Times described it as "more sharply worded than his usual lyrical prose".

The Democratic nominee "presented some long-standing and fairly conventional Democratic economic proposals," according to the Wall Street Journal.

USA Today said the four-day convention in Denver, Colorado, ended "with a display of fireworks and pageantry worthy of an Olympic opening".

But the McCain campaign was unimpressed, with spokesman Tucker Bounds denouncing it as a "misleading speech that was so fundamentally at odds with the meagre record of Barack Obama".

In his televised address, Mr Obama confronted head-on every criticism made by Mr McCain and the Republicans of his campaign and the Democrats, from his ego and rock star status to his lack of foreign policy experience and his tax policies.

"America, we are better than these last eight years," he said. "We are a better country than this.

"This moment - this election - is our chance to keep, in the 21st century, the American promise alive."

The 47-year-old Illinois senator said Mr McCain, a former Vietnam prisoner of war, had "voted with George Bush 90% of the time".

"I don't know about you, but I'm not ready to take a 10% chance on change," he said.

Meanwhile, John McCain's choice of Alaska's first female governor as his running mate was endorsed by President Bush, who said it showed "why the American people can trust him to make wise decisions and to confidently lead this country."

Sarah Palin is virtually unknown outside Alaska, where she has a reputation for government reform and an approval rating higher than 80%.

But Democrats said it was a "very risky" move, one which could leave the inexperienced mother-of-five leading America if anything should happen to Mr McCain.

Mrs Palin wasted no time in going after Hillary Clinton's female supporters. To huge cheers at a raucous rally in Dayton, Ohio, she said she wanted to honour the former first lady who had shown "such determination and grace in her presidential campaign".

Whoever wins on November 4, America will either have its first black president or its first female vice-president in history.

Mr McCain said he made his pick after looking for a political partner "who can best help me shake up Washington and make it start working again for the people who are counting on us".