China, Germany and South Africa criticise US stimulus
Germany, China, Brazil and South Africa have criticised US plans to pump $600bn (£373bn) into the US economy.
German Finance Minister Wolfgang Schaeuble said the US policy was "clueless" and would create "extra problems for the world".
The US Federal Reserve could weaken the US dollar and hurt exports to America.
China's Central Bank head Zhou Xiaochuan urged global currency reforms, while South Africa said developing countries would suffer most.
He did not elaborate how the system should be changed.
'Undermining the G20'
South Africa's finance minister Pravin Gordhan warned that "developing countries, including South Africa, would bear the brunt of the US decision to open its flood gates without due consideration of the consequences for other nations."
The US policy "undermines the spirit of multilateral co-operation that G20 leaders have fought so hard to maintain during the current crisis," he said.
The heads of state and government of the G20 group of the world's leading nations is due to meet in a week in South Korea, with currencies and trade imbalances high on the agenda.
The US central bank announced on Wednesday that it would spend $600bn to buy government bonds, in the hope that the cash injection can kickstart the country's economy.
However, this weakens the dollar, making imports from around the world more expensive for US consumers.
"If the domestic policy is optimal policy for the United States alone, but at the same time it is not an optimal policy for the world, it may bring a lot of negative impact to the world," said Mr Zhou.
"There is a spill over."
China's Vice Foreign Minister Cui Tiankai said the Federal Reserve had the right to take steps without consulting other countries beforehand, but added: "They owe us some explanation."
Germany's finance minister Wolfgang Schaeuble said on German television that "with all due respect, US policy is clueless."
"It is not that the Americans have not pumped enough liquidity into the market and now to say let's pump more into the market is not going to solve their problems."
He added that the German government was going to hold bilateral talks with US officials and also discuss the topic at the G20 summit in Seoul next week.
On Thursday, Brazil's finance minister Guido Mantega had warned that the Fed's move would hurt Brazil and other exporters.
The latest move by the Fed has been dubbed QE2 as it follows the central bank's decision to pump $1.75tn into the economy during the downturn in its first round of quantitative easing.