HONG KONG - China is expected to be a centerpiece of the third and final U.S. presidential debate on Monday night, and my colleague David Sanger, in a curtain-raiser, calls China "perhaps the most important long-term subject of the debate."

Mitt Romney, the Republican challenger, has charged that President Barack Obama has not pressed China hard enough on its trade policies, to the detriment of American firms and jobs. Mr. Obama has countered by calling Mr. Romney "a pioneer of outsourcing" and noting that his administration has brought twice as many trade cases against China as the previous administration.

The United States scored a victory in one of those trade cases last week, as a World Trade Organization panel ruled against China for imposing unfair tariffs on American-made specialty steel. The steel in question was manufactured at two factories - AK Steel of Ohio and ATI Allegheny Ludlum of Pennsylvania.

The W.T.O. ruling could well help Mr. Obama's electoral chances in those key states.

"This is a victory for the United States as well as for American workers and manufacturers," said Ron Kirk, the U.S. trade representative, adding that "China's unfair duties choked off nearly all" of the U.S. exports of the special rolled steel.

"The Obama administration," Mr. Kirk said, "will not stand by and allow China to break international trade rules."

Mr. Kirk's statement and some background on the case are here. The W.T.O. panel's ruling is on its Web site here.

James L. Wainscott, the chairman, president and C.E.O. of AK Steel, said in a statement that the company was "very grateful" to Mr. Kirk's office for "this excellent defense of the rights of U.S. manufacturers and U.S. workers."

The administration filed the case in 2010, and the W.T.O. ruled against China in June of this year. The Ministry of Commerce in Beijing quickly appealed that decision, but the latest ruling effectively settles the matter.

"We are pleased that China at this point has no further avenue for appeals," Mr. Wainscott said.

Derek Scissors, a research fellow at the Heritage Foundation, the conservative policy-research group, said in a Reuters report that the ruling was "a small benefit for the Obama campaign because it can advertise 'beating China' in Ohio, but it's not a benchmark for anything."