CHAPEL HILL, North Carolina — US President Barack Obama told debt-laden students Tuesday he had walked in their shoes, as he sought to connect to Americans hurting in a tough economy, in an apparent dig at Republican Mitt Romney.

Obama, opening a tour of three university campuses in three swing states crucial to his hopes of reelection in November, told a raucous 8,000 strong crowd that he and his wife Michelle had only paid off their student loans eight years ago.

"We had a mountain of debt. When we married, we got poorer together," Obama said, at the University of North Carolina.

"We added up our assets and there were no assets. And we added up our liabilities and there were a lot of liabilities, basically in the form of student loans."

Obama is seeking to show middle class voters, still struggling with the fallout from the deepest recession since the Great Depression that he understands their struggles, and implicitly compares his experience with that of multi-millionaire Romney.

"This is something Michelle and I know about firsthand. I just wanted everybody here to understand -- I didn't just read about this," Obama said.

"I didn't just get some talking points about this. I didn't just get a policy briefing on this. Michelle and I, we've been in your shoes. Like I said, we didn't come from wealthy families."

Obama did not mention Romney, a former venture capitalist and son of auto executive and Michigan governor George Romney by name, but his frequent descriptions of his less than privileged upbringing seem a clear attempt to draw contrasts to his rival.

Last week, Obama caused a minor political storm when he said he was "not born with a silver spoon" in his mouth.

White House officials vehemently denied that Obama was trying to single out Romney with the quote, saying he had used it many times before.

But Romney, like Obama a graduate of Harvard Law school, told Fox News that Obama liked to "attack fellow Americans" and said he was not going to apologize for the success of his father.

That prompted Obama's spokesman Jay Carney to dig back at the former Massachusetts governor saying he was perhaps a little "over sensitive."

Obama, taking at the youth vote that could be crucial in November's presidential election, was due to hold another speech at a university in Colorado on Tuesday, before heading to another important electoral battleground, Iowa on Wednesday.