SEOUL, South Korea — The Group of 20 major economies took initial steps to address imbalances in the global economy on Friday. But they did not act as assertively as President Obama had hoped, and he left little doubt that he considered one country, China, the primary source of the problem.

Scrapping a longtime practice of speaking with diplomatic caution about China’s currency policy, Mr. Obama accused Beijing of intervening aggressively to keep its currency, the renminbi, below its market value to promote exports. He said it was a mistake for nations to think that “their path to prosperity is paved simply with exports to the United States.”

“Precisely because of China’s success, it’s very important that it act in a responsible fashion internationally,” Mr. Obama said at a news conference at the conclusion of the economic summit meeting here. “And the issue of the renminbi is one that is an irritant not just to the United States, but is an irritant to a lot of China’s trading partners and those who are competing with China to sell goods around the world.”

Though his own Treasury Department, like those of prior administrations, has certified that China is not a “currency manipulator,” a designation that can prompt Congressional trade action, Mr. Obama appeared to remove the remaining wiggle room he had on the subject of the renminbi, declaring: “It is undervalued. And China spends enormous amounts of money intervening in the market to keep it undervalued.”

The tougher language seems likely to add tension with China, which has already sharply criticized the Obama administration’s decision to try to mediate territorial disputes involving China and its East and Southeast Asian neighbors.

But Mr. Obama’s efforts to persuade China to act on its own, or as part of a collective commitment by big economies to address trade imbalances, have yielded only incremental steps, raising the possibility of a contentious and awkward prelude to a state visit to Washington by President Hu Jintao of China scheduled for January.

http://www.nytimes.com/2010/11/13/business/global/13group.html?_r=1&hpw=&pagewanted=print