Obama asks supporters to keep the faith

With just two months before election day, Mr Obama needs to win over undecided voters, especially those who had been swayed by his inspiring message of hope and change in 2008, but now feel disillusioned after years of economic weakness and persistent political bickering.

"The election four years ago wasn't about me. It was about you," he said. "My fellow citizens - you were the change."

He said the American people were the ones responsible for accomplishments on his watch, such as overhauling health care, changing immigration policies and ending the ban in gays in the military.

If they turned away now, he warned, "you buy into the cynicism that the change we fought for isn't possible. "Change," he said, "will not happen".

Mr Obama built on the message Democrats delivered throughout the convention: that America is on the road to recovery while Mr Romney would revive failed policies, cutting taxes for the rich and slashing programmes that give regular Americans a chance for a more prosperous future.

"If you reject the notion that this nation's promise is reserved for the few, your voice must be heard in this election," he said.

Republicans, who nominated Mr Romney last week, argue that America's high 8.3% unemployment rate is proof that Mr Obama's policies have failed and that the president's spendthrift, big-government policies have hurt business and caused the federal deficit to soar.

The two candidates are locked in a tight race. Polls show that Mr Romney, a wealthy businessman and former governor of Massachusetts, is seen as the better candidate for improving the economy, while Mr Obama is viewed as more likeable and having a better understanding of everyday Americans.

Mr Obama's speech marked the climax of the three-day convention. First lady Michelle Obama highlighted the first day, talking about her husband's humble roots and compassion for those living through tough times.

Bill Clinton, the popular former president who led the United States during years of prosperity, gave a rousing speech yesterday, vouching for Mr Obama's economic policies and urging Americans not to turn back to Republicans.

Preceding Mr Obama was Vice President Joe Biden, who was formally re-nominated. Mr Biden proclaimed in his acceptance speech that "America has turned the corner" after experiencing the worst economic crisis since the Great Depression.

Mr Obama needed to strike a balance in his speech, highlighting improvement in the economy without suggesting that things are fine as they are.

Democrats argue that the economy would be worse if it hadn't been for Obama-led programmes to rescue the car industry and stimulate the economy. Still, it is difficult to win over voters by arguing that things could have been worse.

Mr Obama set out a goal of creating one million new manufacturing jobs by the end of 2016 and push for more aggressive steps to reduce American dependence on foreign oil.

Though the economy has dominated the convention, Democrats have also discussed national security issues, where Mr Obama does well in polls. They highlighted his carrying out his promise to pull US combat forces from Iraq and, especially, his order that led to the killing of terrorist leader Osama bin Laden.

Mocking a Republican slogan asking Americans if they are better off under Mr Obama, John Kerry, the Democratic presidential nominee in 2004, told delegates: "Ask Osama bin Laden if he's better off now than he was four years ago."

Mr Obama also noted that both Mr Romney and his vice presidential running mate Paul Ryan have little foreign policy experience.

"They want to take us back to an era of blustering and blundering that cost America so dearly," he said.

He said Mr Romney was "stuck in a Cold War time warp" for describing Russia - not al Qaida - as America's number one enemy.

Recalling the stir Mr Romney caused during a visit to London by questioning British preparations for the Olympics, Mr Obama said: "You might not be ready for diplomacy with Beijing if you can't visit the Olympics without insulting our closest ally."

Yet after the defence of his policies and the foreign policy jibes came the soaring rhetoric that once captured America's imagination and propelled Mr Obama's rapid rise from local politician in Illinois to becoming the first black president of the United States.

"America, I never said this journey would be easy, and I won't promise that now," he said.

"Yes, our path is harder - but it leads to a better place. Yes our road is longer- but we travel it together. We don't turn back. We leave no one behind. We pull each other up. We draw strength from our victories, and we learn from our mistakes, but we keep our eyes fixed on that distant horizon, knowing that providence is with us, and that we are surely blessed to be citizens of the greatest nation on earth."

The delegates erupted in cheers, some with tears in their eyes. Michelle Obama and the couple's daughters, Malia and Sasha, joined the president on stage, followed by other family members, Mr Biden and his wife. Strains of Only in America filled the hall as confetti filled the air.

Mr Obama needed to fire up not only undecided voters, but also his party's base as he tries to fatten his campaign coffers.

Mr Romney and Republicans have a strong lead in fund-raising, a striking reversal from 2008 when Mr Obama held an overwhelming advantage over then-rival John McCain.

Independent groups seeking Mr Romney's election are pouring tens of millions of dollars into television advertising, far exceeding what Mr Obama's supporters can afford.

Citing a chance of thunderstorms, convention organisers scrapped plans for Mr Obama to speak to an enormous crowd in a 74,000-seat outdoor stadium and decided to shoehorn the event into the convention arena, which accommodates 15,000.

That meant a far smaller crowd than the president's campaign hoped would hear him speak and present an enthusiastic show of support on television

Mr Romney was wrapping up several days of rehearsals ahead of an October 3 debate with Mr Obama, the first of three. He is expected to resume full-time campaigning within days.