US President Barack Obama used his first large-scale rally of the 2012 election campaign on Saturday to pledge to continue efforts to move the economy forward if given a second term. In a direct attack on rival Mitt Romney, Obama warned that the republican candidate would reverse positive economic progress.

"We are not turning back the clock, we are moving forward," Obama told a fired-up crowd in Ohio, a likely battleground state in the Nov. 6 election.

Addressing an estimated 10,000 supporters at Ohio State University in Columbus Obama said Romney would "rubber stamp" some "bad ideas" such as tax cuts for the rich, while slashing spending on social programs that benefit the embattled middle classes.

"Ohio, I tell you what, we cannot give him that chance... 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 added.

Tight race ahead

Six months before Election Day the polls point to a close race between Obama and Romney.

As the US struggles to recover from the worst financial crisis since the 1930's the economy is fast becoming the overriding theme of the presidential campaign. Although unemployment has receded slowly and evenly, having peaked several months into the president's term, it remains high at 8.1 percent nationally.

As a successful businessman, Romney has staked his candidacy on an understanding of the economy and has promised to boost growth and implement policies that stimulate job creation. But on Saturday, Obama sought to use Romney's business credentials as proof he would not be able to relate to the average American.

Romney "doesn't seem to understand that maximizing profits by whatever means necessary, whether it's through layoffs or outsourcing or tax avoidance, union busting, might not always be good for the average American or for the American economy," the president said.

"Why else would he want to cut his own taxes while raising them for 18 million Americans," Obama said of his multimillionaire opponent.

Crucial swing states

Obama formally launched his re-election effort last year and has attended numerous fundraises in 2012. The White House, however, has categorized all of his other appearances as part of his official presidential duties, making the Ohio the first fully-fledged political rally of the election year.

More rallies are expected to follow in the coming months in swing-states like Florida, where the presidential candidates will compete for independent or undecided voters.

ccp/nrt (AFP, AP, Reuters)