Mr. Obama spoke at a news conference at the end of a nuclear security summit in Washington where the two leaders met on April 12 for the first time since Sino-U.S. tensions over the yuan had threatened to escalate into a serious dispute.

"With respect to the currency issue, President Hu and I have had a number of frank conversations," he told reporters. In diplomatic terms, the word "frank" typically means neither side held back.

"I have been very clear of the fact that it is my estimation that the RMB (yuan) is undervalued, and that China's own decision in previous years to begin to move toward a more market-oriented approach is the right one," Mr. Obama said.

"So I don't have a timetable, but it is my hope that China will make a decision that will ultimately be in their best interest."

Mr. Hu did not make public remarks on the yuan in Washington on April 13, but Vice Foreign Minister Cui Tiankai reiterated Hu's assertion the previous day that the currency decision was an "internal affair" and would be made based on China's economic situation.

"On this issue it is not justified for outsiders to exert pressure and we will not take action by bowing to this pressure," Cui told a news briefing in Washington.

Blaming China's exchange rates for global economic problems is "just a like a situation where you have caught a cold, but ask your neighbor to take the medicine," Cui added, in China's latest public pushback against U.S. pressure over the yuan.

The two leaders chose their words carefully over the two-day summit and, in the view of investors, left the door open for Beijing to resume appreciation of the currency in coming weeks.

Many mainstream economists believe the currency is undervalued by as much as 40 percent and that China's massive current account surplus shares blame with the U.S. deficit for financial imbalances behind the global economic turmoil.