Complaints over the yuan's value have eased over the last two months as the euro crisis ran deep, but they resurfaced after China's trade surplus posted a surge of 48.5 percent in May from a year earlier, giving China a trade surplus of $19.5 billion, up from just $1.7 billion in April.

US data showed that its trade deficit widened slightly in April, with some economists arguing that the improvement in net trade and its contribution to US growth appeared to have stalled.

Zuo Xiaolei, chief economist of China Galaxy Securities, noted that some forecasts of Chinese trade figures are based on plausible analyses, which overestimate the European debt crisis' impact on China and doesn't account for its lagged effect.

In fact, she said, the hike of exports in May was because of a low comparison basis from the same period last year, which decreased by 25.9 percent.

Meanwhile, the growth of imports from the US and EU in May exceeded the rise of exports to these areas.

The mounting pressure of wage increases in some export-oriented companies also shows that the appreciation of China's currency, with export prices hard to be raised, can only reduce the room for labor income growth, she added.

Limited impact

Even if the yuan is as much as 40 percent undervalued against the dollar and is allowed to appreciate, the impact on US companies would be limited, perhaps increasing prices of Chinese goods around 10 percent, Marc Chandler, the global head of currency strategy at Brown Brothers Harriman & Co, told the Wall Street Journal (WSJ).

John Frisbie, head of the US-China Business Council, said a political move by Congress would be mostly counterproductive, as legislation required to counter misaligned currencies would violate World Trade Organization rules, according to the WSJ.

Also, the US hasn't acknowledged China's market-economy status, though it did pledge during the strategic talks with China last month to seriously con-sider the issue and speed up the process, which is sure to face obstacles in the US Congress.

China has already stated that it would take both the international and domestic economic situation into consideration when it comes to deciding the timing of any change in the yuan's value, and it will commit to the exchange-rate reform at its own pace.