Washington, Sep 18 (IANS): With just 50 days to go for what is expected to be a close presidential race, President Barack Obama played the China card against his Republican challenger Mitt Romney with another outsourcing jab.

"I like to walk the walk, not just talk the talk," said Obama Monday at a campaign event in Cincinnati, Ohio, a crucial swing state, announcing his administration's new trade enforcement case against China in the World Trade Organisation.

Obama's re-election campaign also released a new television ad criticising Romney for opposing his tough stance on China while renewing Obama's charge that as head of investment firm Bain Capital, Romney was an "outsourcing pioneer" who shipped American jobs to countries like India and China.

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

"And my experience has been waking up every single day and doing everything I can to make sure American workers get a fair shot in the global economy."

"We don't need folks who during election time suddenly are worrying about trade practices, but before the election are taking advantage of unfair trading practices," Obama says.

In the new Obama ad, following a clip of Mitt Romney promising to crack down on China's trade policies, the ad's narrator says, "Tough on China? Not Mitt Romney."

Then citing a 2009 US International Trade Commission Federal Register Notice, the ad narrator says, "When a flood of Chinese tyres threatened a thousand American jobs it was President Obama who stood up to China and protected American workers."

Pointing to media reports about Obama imposing stiff tariffs on Chinese-made tyres to protect America jobs, he continues: "Mitt Romney attacked Obama's decision.said standing up to China was 'bad for the nation and our workers'."

The ad concludes by questioning whose side Romney is on pointing to an excerpt from Romney's book "No Apologies" where he criticises the trade case filed on behalf of US tyre manufacturers saying it could spark a trade war.

The Romney camp earlier dismissed Obama's latest trade challenge to China as "politically motivated" and "too little, too late".