President Barack Obama Wednesday mocked Mitt Romney's get tough with China rhetoric, saying his foe's record of making money in China meant he would be like a fox guarding a chicken coop.

Obama and Romney clashed on trade with the giant Asian economy at dueling political events in Ohio, a key midwestern swing state which has seen thousands of blue collar jobs migrate to low cost economies abroad, including China.

"He's been talking tough on China," Obama said of his White House challenger at an event in the college town of Bowling Green.

"He says he's going to take the fight to them; he's going to go after these cheaters," Obama said, before accusing Romney of spending years investing some of his money in US firms that outsourced jobs to China.

"When you hear this newfound outrage, when you see these ads he's running promising to get tough on China, it feels a lot like that fox saying, 'You know, we need more secure chicken coops.'"

"I mean, it's just not credible."

Romney hit northern Ohio as part of a bus tour and renewed his vow to stop China from stealing American jobs with unfair trade practices as he wooed blue-collar workers and business owners.

He lambasted Obama for failing to prevent the loss of 582,000 manufacturing jobs in the past four years and placed much of the blame for the industry's decline on "competition from overseas, which is often unfair."

"From day one I will label China as a currency manipulator," Romney told supporters gathered in a spring wire plant in suburban Cleveland.

"They must not steal jobs."

Obama however touts a string of complaints and actions he has leveled against China at the World Trade Organization, including a case against Chinese auto and auto parts subsidies that he unveiled in Ohio last week.

In a new web video, the Obama campaign accused Romney of investing in YouKu, the Chinese equivalent of YouTube, which it described as a haven for stolen US videos and of backing a Chinese firm accused of pirating Microsoft software.

"If Romney really wanted China to stop stealing, why would he send them his money?" the ad's narrator asked.