Barack Obama at DNC
US President Barack Obama celebrates with first lady Michelle Obama after accepting the 2012 US Democratic presidential nomination during the final session of the Democratic National Convention in Charlotte. - Reuters

Accepting his official nomination for a second term, President Barack Obama made a passionate appeal to US citizens to re-elect him in the November elections - saying he has unfinished business in the White House.

Obama said it needs more time to solve problems that have been piling up for decades, telling his audience: "You didn't elect me to tell you what you wanted to hear. You elected me to tell you the truth. The truth is, it will take more than a few years for us to solve challenges that have built up over decades.

"I won't pretend the path I'm offering is quick or easy. I never have. But when you pick up that ballot to vote - you will face the clearest choice of any time in a generation."

Obama's televised speech at the Democratic National Convention at Charlotte was watched by millions of people across the world.

His address follows a fervent plea by former Democrat president Bill Clinton, who asserted that Obama inherited a weak economy.

Obama Clinton
Obama talks into Bill Clinton's ear on stage. [Reuters]

Referring to his agenda, Obama said: "Over the next few years, big decisions will be made in Washington, on jobs and the economy; taxes and deficits; energy and education; war and peace - decisions that will have a huge impact on our lives and our children's lives for decades to come."

Obama is facing tough questions on his economic policies. Over the next few weeks, he will be seen debating with Republican contender Mitt Romney.

Obama kids
Obama walks around the stage with his wife and children. [Reuters]

Same old recipe

Tackling the Republicans head on, Obama said they have nothing new to offer except repeating the same old formula.

"That's because all they have to offer is the same prescription they've had for the last thirty years. Have a surplus? Try a tax cut. Deficit too high? Try another. Feel a cold coming on? Take two tax cuts, roll back some regulations, and call us in the morning!"

Obama wife
Barack Obama hugs wife Michelle in front of enraptured voters. [Reuters]

Vice President Joe Biden, who is also running for his second term, stressed the impact of Obama's policies on American families. "Folks, I've watched him. He never wavers. He steps up. He asks the same thing over and over again: How is this going to work for ordinary families? Will it help them?"

Scores of other leaders strongly pitched for Obama on the third night of the convention.

Responding to Obama's speech, the Republican camp said he had failed to keep the promises he made four years ago and was bent on carrying on with the same policies that, it says, have failed.

Obama supporters
Obama's appearance brought a fervent response from the audience. [Reuters]