WASHINGTON - The Wall Street Journal on Saturday criticized Republican presidential nominee Mitt Romney for playing protectionism in a latest campaign ad that slams President Barack Obama for failing to stop the so-called "China's cheating."

"Yet a bona fide protectionist hasn't won the White House since the 1920s. The reason is because voters instinctively want a President who knows how to make America more competitive, not one who campaigns as if other countries are more formidable," wrote an editorial published by the paper.

In the Romney's campaign ad, titled "Failing American Workers," the US flag is shown to begin to shrink while the Chinese flag grows, signaling that 582,000 US manufacturing jobs have been lost to China since Obama became President. It claimed that, for the first time, "China is beating us" as the world's leading manufacturing country.

Romney, who promises to designate China as a currency manipulator on the first day of office if elected, has repeatedly blasted Obama for failing to punish China. "Seven times, Obama could have stopped China's cheating. Seven times, he refused," the ad claimed.

Romney's "China-bashing" is especially odd for the candidate, because he "professes elsewhere that he wants to expand trade because it will create jobs," the article said, noting that China is a major trade partner of the US.

Protectionism is also not the way to make the case for reducing trade barriers, as it was demonstrated in the move by former President George W. Bush in 2001 to impose steel tariffs as a way to get trade promotion authority from Congress to negotiate and pass the Doha trade round, the article wrote.

Trade authority passed, but Doha died, in part because the rest of the world resented the steel tariffs and Bush's 2002 protectionist farm bill, it noted.

"As a former businessman, Mr Romney surely knows that cheaper Chinese imports create jobs in the US up and down the merchandise and services value chain," the article said, referring to a recent Heritage Foundation study that finds that the imports from China support nearly 600,000 American jobs in the apparel and toy industries alone.

Plenty of studies also recognize that "Made in China" often has more to do with final assembly than with original content and intellectual value-added, it added.

"Mr Romney's larger mistake is that this ad conveys an economic pessimism that undermines his political case that he can deliver a better future for American workers. If the only way to revive American manufacturing is to steal jobs back from China, our future can't be very bright," it wrote.