U.S. President Barack Obama is seeking to rally his base of support among 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 is in Toledo, Ohio, in the heart of the industrialized central part of the U.S., for a Monday rally of unionized auto workers on Labor Day, a national holiday saluting U.S. workers. Toledo is home to both General Motors and Chrysler manufacturing plants that benefited from his support of a massive government bailout of the auto industry in 2009 as it struggled from foreign competition in the worldwide economic downturn.

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.