A strong sense of pessimism has shrouded the first day of the G20 summit of rich and emerging economies, with world leaders sharply divided over currency and trade policies.
The US clashed with exporting giants China and Germany on Thursday over a plan to rebalance skewed trade between deficit and surplus countries.
The summit, held in Seoul, South Korea's capital, has become the centrepiece of international efforts to revive the global economy and prevent future financial meltdowns.
Behind the scenes, negotiators squabbled over the language in a closing statement to be issued at the summit's conclusion on Friday, but so far, officials cannot even agree on the agenda, much less a draft statement.
Barack Obama, the US president, who is working to salvage a deal at the summit after suffering an economy-linked drubbing in US elections last week, said his administration wanted to boost growth via "prudent" economic policies.
"It is difficult to do that if we start seeing the huge imbalances redevelop that helped to contribute to the crisis that we just went through," he told a news conference with the summit's host, Lee Myung-Bak, the South Korean president.
"I don't think this is a controversial proposition."
Several G20 members are upset after the US Federal Reserve's decision to pump a further $600bn into the faltering US economy, in a step that foreign critics say is likely to trigger tit-for-tat currency devaluations.
Chinese officials sought to throw the onus back on the US by arguing that Beijing has an "unswerving" commitment to reform its currency regime, but needs stability in the world economy to do it.
"If you're sick yourself, don't ask others to take medicine," Yu Jianhua, the commerce ministry spokesman, said, demanding the debt-ridden US fix its own house first.
In one-on-one talks with Obama, Hu Jintao, the Chinese president, said: "I believe that with the concerted efforts of all the parties, the summit in Seoul will produce positive outcomes."
David Cameron, the UK prime minister, conceded that the G20 was not in a "heroic phase" compared to its determined response to the 2008 financial crisis, and that it needed to do "a lot more work" on fixing economic imbalances.
Harried negotiators have been meeting long into the night all week in Seoul to try to pin down language that the G20 leaders can adopt in the closing communique.
The talks were likely to drag long into Thursday night, South Korean officials said, after the G20 heads of government opened their two-day summit with a working dinner of Korean beef and halibut.
"China is being very difficult in finalising the texts, so there might be brackets left for the leaders to fill in after all," a German government source said on Thursday.
South Korean and German officials said tha at best the G20 may settle for a watered-down deal to task the International Monetary Fund with crafting guidelines to trim the yawning imbalances between creditor and debtor nations.
Ahead of her own bilateral meeting with Obama, Angela Merkel, the German chancellor, lashed out at a more detailed US plan to rectify lopsided commerce by limiting the current account surpluses of big exporters.
The US wants the G20 to agree to curtail "excessive imbalances" as a back-door way of forcing China to realign its currency, which critics say is keeps deliberately cheap to support Chinese exporters.
But the proposal has run into trouble not just from China but from an array of nations including Germany, another export champion that insists its own trading prowess has nothing to do with any currency chicanery.
"To set political limits on trade surpluses and deficits is neither economically justified nor politically appropriate," Merkel told a G20 business summit.
Emerging economies around the world are worried that the billions in new money from the Federal Reserve will stoke speculative flows of foot-loose "hot money", and some are resorting to capital controls in a bid to stem the tide.
There is anxiety that G20 nations could be heading for a return to 1930s-style trade protectionism, with damning consequences for the world economy two years after the start of the global financial crisis.
Naoto Kan, the Japanese prime minister, said the risk was of "competitive devaluation of currencies reminiscent of the Great Depression".