U.S. President Barack Obama is rallying blue-collar factory workers as he heads to this week's Democratic National Convention to be formally nominated for a second term in the White House.

Mr. Obama was in Toledo, Ohio, in the heart of the industrialized central part of the U.S., on Monday to speak to unionized auto workers on Labor Day, a national holiday saluting U.S. workers. Toledo is home to both General Motors and Chrysler manufacturing plants and the president reminded workers that he supported the massive government bailout of the ailing auto industry in 2009 at the height of the global economic downturn.

“I stood with American workers. I stood with American manufacturing. I believed in you. I bet on you. I'll make that bet any day of the week. And because of that bet, three years later, that bet is paying off for America.”

Before heading to Charlotte, North Carolina, for the convention that opens Tuesday, the president is making campaign stops in key states where voter surveys show his contest with Republican challenger Mitt Romney is especially close. Later Monday, Mr. Obama is headed to Louisiana, on the country's southern shoreline, to view storm damage caused by Hurricane Isaac last week.

The U.S. has the world's largest economy, but it has struggled to regain its economic footing. The country's jobless rate remains above an unusually high 8 percent and the sluggish economy has imperiled Mr. Obama's re-election chances. Surveys show him in a virtual tie with Mr. Romney.

The Republican challenger said Labor Day was “a chance to celebrate the strong American work ethic.” But he said that for many jobless Americans it is “another day of worrying” when their next paycheck will come.