US president Barack Obama is challenging his Republican rival Mitt Romney's promises to crack down on China's trading practices.
An advert claims that the Republican candidate profited by allowing China to strip away US jobs.
Mr Obama's ad turns again to a recent Washington Post report that several businesses backed by Mr Romney's former private equity firm moved American jobs to China and India to cut costs. In a parting shot, a narrator says Mr Romney is "not the solution... He's the problem".
The advert follows the president's two-day bus tour in Ohio and Pennsylvania, where he announced plans to file a trade complaint against China at the World Trade Organisation (WTO) for unfairly imposing duties on US-produced cars. Ohio is home to several car factories and tens of thousands of workers directly employed by the industry.
China remains a flashpoint in the presidential campaign.
Mr Romney has accused Mr Obama of failing to live up to promises to get tough on the economic powerhouse, saying he would label China a currency manipulator on his first day in office and fight the theft of intellectual property and job losses. Mr Obama's administration says it has taken a broad effort to crack down on what it calls unfair Chinese trading practices, filing seven trade cases with the WTO against Beijing.
The 30-second TV spot opens with a clip of Mr Romney during a 2011 Republican primary debate. He says: "The Chinese are smiling all the way to the bank taking our jobs and taking a lot of our future. And I am not willing to let that happen." A narrator responds that Mr Romney "made a fortune letting it happen".
The Obama ad refers to the Post's account of the role Mr Romney's firm played with companies that were "pioneers" in helping outsource jobs. It pointed to one business that said it was a "one-stop shop for their outsource requirements". The Obama spot is part of a 25 million dollar (£16 million) ad buy in July and will run in New Hampshire, Virginia, North Carolina, Florida, Ohio, Iowa, Colorado and Nevada.
Mr Romney spokeswoman Andrea Saul said it was "no surprise president Obama would want to distract Americans from the devastating June jobs numbers, but the American people deserve better than dishonest ads". Mr Romney's campaign has questioned the accuracy of the report and asked the Post for a retraction. The newspaper stood by its report.
The ad represents the latest attempt by Mr Obama's team to discredit Romney's argument that his private sector experience makes him more qualified than the president to steer the economy during high unemployment. Mr Obama's campaign has repeatedly cited the recent Washington Post story outlining how several businesses backed by Mr Romney's former firm, Bain Capital, transferred jobs to lower-wage countries such as China and India.