US President Barack Obama has accused Republican foe Mitt Romney of failing to offer "a single new idea" and being a relic of the last century as he revved up a pre-convention tour.
Rattling through battleground states en route to the Democratic National Convention this week in Charlotte, North Carolina, Obama also rebuked Romney for ignoring the Afghan war during his own nominating speech.
"It was something to behold," Obama told a 13,000-strong crowd in Colorado, as he picked apart Romney's keynote address in Florida on Thursday night (local time) that marked the climax of a three-day Republican convention.
"Despite all the challenges we face in this new century, what they offered over those three days was an agenda that was better suited for the last century," Obama said.
"It was a re-run... we have seen it before - you might as well have watched it on a black and white TV with some rabbit ears."
Democrats say that Romney, who used his convention to try to tell his personal story and improve his likeability ratings, may have given Obama an opening by offering only sketchy policy stands.
They are also framing Obama as a candidate of the future, with his slogan "Forward", and to position the older Romney - he is aged 65 while Obama is 51 - as a contender from a bygone era.
Obama said that Romney, with whom he is neck and neck in the polls ahead of the November election, had refused to reveal the "secret sauce" that would help him create jobs: "he did not offer a single new idea".
"It was retreads of the same old policies we have been hearing for decades, the same politics that have been sticking it to the middle class for years," the president added.
He also said Romney had "nothing to say" in his speech in Florida about the Afghan war, which the president has promised to end "responsibly" in the same way that he brought troops home from Iraq.
"We are bringing our troops home from Afghanistan. And I set a timetable - we will have them out of there by 2014. Governor Romney doesn't have a timetable. I think he is wrong."
Romney has criticised setting a withdrawal date for US forces, saying doing so would aid US enemies.
But he has also suggested that the "right timetable" for a withdrawal is by the end of 2014 - a date already set by NATO.
Obama is on a four-day "Road to Charlotte" tour taking in territory that will decide November's election, in which his prospects are clouded by a painfully slow economic recovery and 8.3 per cent unemployment.
He started in Iowa, the state that nurtured his unlikely 2008 presidential run and where he is now locked in a tight race with Romney.
After Colorado, the president heads to Ohio to celebrate the Labor Day holiday with working Americans on Monday.