Obama begins campaign with rallies in Ohio and Virginia
US President Barack Obama has kicked off his campaign for re-election in November with rallies in two key battleground states, Ohio and Virginia.
He told supporters in Ohio that the US had been fighting back from recession and pledged further efforts on the economy if given a second term.
He hit out at his rival Mitt Romney, saying the Republican challenger would "turn back the clock".
But he also acknowledged that the 6 November vote would be tight.
He said he understood that many in the country are dissatisfied with the slow pace of the change he promised when he came to power.
On Friday, Mr Obama fended off criticism from Mr Romney over disappointing job figures. The jobless rate in the US has been stuck above 8% since early 2009.
Official figures showed that the US economy created 115,000 jobs during April, down on the previous month and fewer than analysts had expected.
President Obama strolled on stage in Columbus, Ohio, to cheers and chanting from thousands of supporters already warmed up by glitzy campaign videos and an introduction from his wife Michelle.
Confronting his critics head-on, he reminded the audience that he had inherited the financial crisis. He said he acknowledged that many Americans were still hurting, but urged voters to give him a second term to continue making progress.
"This is not just another election, this is a make or break moment for the middle class. We have been through too much to turn back now," he said to some 14,000 supporters in a sports arena.
"That's the choice in this election and that is why I am running for a second term as president of the United States," Mr Obama said.
The audience erupted into chants of "four more years".
Mr Obama described Mr Romney as a good family man and businessman, but said he had learned the "wrong lessons" from being a CEO, saying his policies would only benefit the wealthy.
"I think he has drawn the wrong lessons from those experiences. He sincerely believes that if CEOs and wealthy investors like him make money the rest of us will automatically prosper as well."
A spokeswoman for Mr Romney said in response: "While President Obama all but ignored his record over three-and-a-half years in office, the American people won't. This November, they will hold him accountable for his broken promises and ineffective leadership."
Mr Romney had no public campaign events on Saturday.