NEW YORK (Bloomberg) — The US has a "special responsibility" to support the dollar as a reserve currency, US Treasury Secretary Timothy Geithner said, reaffirming the country's foreign exchange policy stance.

"It is the policy of the United States to support a strong dollar," Geithner told reporters on Saturday after a meeting of Group of 20 finance ministers and central bankers in Gyeongju, South Korea.

"We in the United States recognise the special responsibility we have" to support global financial stability and the dollar's role in the world economy, he said.

Geithner's remarks came after G-20 finance officials took a joint stance on exchange rates as they sought to end concern that nations from the US to China are relying on cheap currencies to spur growth, risking a protectionist backlash.

The US also heard "criticism" from within the group about the effects of possible further monetary easing, said German Economy Minister Rainer Bruederle.

Geithner declined to comment on quantitative easing or Federal Reserve policy. The G-20 agreed to "move towards more market determined exchange rate systems that reflect underlying economic fundamentals and refrain from competitive devaluation of currencies," according to its post-meeting statement.

European Central Bank President Jean-Claude Trichet said he was "impressed" with Geithner's comment that the US government doesn't intend for the dollar to be weak.

"A strong dollar is in the interest of the United States of America," Trichet said today at a separate news conference after the G-20 meeting. "This is a sentiment that we share."

Turning to China's currency, Geithner said it was important that the country continues with "very promising" efforts to allow a strengthening of the yuan. The nation played a "very constructive" role in this week's G-20 talks, he said.

In his prepared remarks, Geithner said the global economy still faces "very substantial economic challenges" and he called for a continued "gradual" appreciation of emerging-market currencies against their advanced economy counterparts.

"Countries with significantly undervalued exchange rates committed to move towards more market-determined exchange-rate systems that reflect economic fundamentals, as China is now doing," he said.

The Treasury chief said Saturday's agreement among G-20 nations will ease pressure on emerging markets to add foreign-exchange controls to protect economic growth.

"We all committed to refrain from competitive devaluation, or undervaluation," Geithner said. "These commitments should help reduce some of the pressure being experienced by those emerging economies that are appropriately running more flexible exchange-rate systems and have already seen their currencies move significantly higher."