CINCINNATI - President Obama today sharpened a personal line of attack on his Republican rival, mocking Romney's tax proposals and renewing a charge that he is an outsourcing "pioneer."

"I've actually done my own taxes," Obama said, showing a hint of disdain for Romney at a rally in Eden Park. "I don't know about some of these other folks, but I've done them, you know… So I know we can make it more simple and more fair."

The president blasted the Romney-Ryan tax plan as slanted toward upper-income earners, increasing burdens on the middle class and growing the federal deficit. "As President Clinton pointed out, there's one thing missing from it: arithmetic. Arithmetic," Obama said.

"They must have skipped math class when they were in school," he quipped of his opponents. "And whenever you ask them to explain the plan, they won't. They won't say how they pay for $5 trillion in new tax cuts. They can't tell you how they're going to pay for it. And the truth is, they can't pay for it without raising taxes on middle-class families."

Obama made his jibe at Romney's lack of specifics as the Republican camp recalibrates Romney's message and promises a more specific economic plan.

The president derided Romney for what he described as blind adherence to a tax-cut focused approach to the economy, no matter the situation.

"The plan they've got is the same one that they've been offering for decades," Obama said. "You want to make a restaurant reservation or book a flight? You don't need the new iPhone. Try a tax cut. Try and drop a few extra pounds? Try a tax cut. They've got one answer for everything."

Turning to trade policy with China, Obama swiped back at Romney for a debate that has been intensely playing out on the state's TV airwaves over the past few weeks. Romney has accused Obama of "not going to the mat" for American workers by failing to aggressively address alleged unfair and illegal trade practices by the Chinese.

"He's been running around Ohio claiming he's going to roll up his sleeves and he's going to take the fight to China," Obama said of his rival in a mocking tone. But "his experience has been owning companies that were called pioneers in the business of outsourcing jobs to countries like China. He made money investing in companies that uprooted from here and went to China. Pioneers.

"Now, you can't stand up to China when all you've done is sent them our jobs," Obama said. "You can talk a good game, but I like to walk the walk, not just talk the talk."

Obama announced that the administration had today filed a complaint against China with the World Trade Organization today alleging improper subsidies for auto and auto-parts suppliers, making it more difficult for American companies to compete in the global marketplace. It's the eighth such case filed by the administration in the past four years.

Republicans pushed back on Obama's portrayal of his record, pointing to criticism from high-profile Democrats of the administration's approach to China during the entirety of the president's term. Sens. Sherrod Brown of Ohio, Chuck Schumer of New York, Bob Casey of Pennsylvania, and Rep. Tim Ryan of Ohio - all Democrats - have made comments this year urging Obama to be more aggressive in its effort to confront China on trade rules violations and currency manipulation.

The Republicans also claimed that the actions have failed to significantly improve economic conditions in Ohio and across the country.

"President Obama is recycling false and debunked attacks because he can't tell the people of Ohio about his record of fewer jobs, more debt, and lower incomes," said Romney campaign spokesman Ryan Williams. "It's middle-class Americans who have paid the real price for President Obama's weak, ineffective leadership."