June 11 (Bloomberg) -- China's trade surplus rose a bigger- than-estimated 73 percent in May from a year earlier, increasing pressure on the government to allow faster currency gains.

The gap widened to $22.5 billion, the customs bureau said on its Web site. The median estimate of 18 economists surveyed by Bloomberg News was for a $19.5 billion surplus. For the first five months, the surplus grew 84 percent to $85.72 billion.

Surging exports spurred economic growth of 11.1 percent in the first quarter and drove foreign-exchange reserves to a record $1.2 trillion. A stronger yuan would ease tensions with trading partners and help prevent the world's fastest-growing major economy from overheating.

``Today's number is very large and will add political pressure for currency gains,'' said Sebastien Barbe, senior economist at Calyon in Hong Kong. ``Also, the Chinese government needs to look for new ways to cool the economy, investment and the stock market -- and the currency is becoming a very big part of that.''

Exports rose 28.7 percent from a year earlier. Imports increased by 19.1 percent. The April surplus was $16.9 billion.

The yuan's rise has stalled since Chinese and U.S. officials met for trade talks in Washington last month. The currency dropped to 7.6632 per dollar in Shanghai today, bringing losses in the past three days to 0.36 percent. It has gained 1.8 percent so far this year. By contrast, India's rupee is up 8.5 percent.

U.S. Legislation

U.S. senators will unveil legislation on June 13 to pressure China to revalue its currency. The legislation, sponsored by Charles Schumer, a New York Democrat, lays out U.S. responses when countries ``including China unfairly undervalue their currency,'' according to a statement released by four senators today in Washington.

European Central Bank President Jean-Claude Trichet said last week that China should make its currency more flexible, a view echoed today by Japan's Finance Minister Koji Omi. French President Nicolas Sarkozy has criticized the Chinese government for the pace of yuan appreciation.

Some U.S. lawmakers said last month that the yuan was undervalued by 40 percent to make China's exports cheap and pledged trade sanctions as punishment.

``Americans are impatient to see real change,'' U.S. Treasury Secretary Henry Paulson said June 5. ``A large section of the American public doesn't believe that the benefits of trade are being shared equally between or within our two countries.''

Yuan's Gains

The yuan has strengthened about 8 percent since China scrapped a 10-year peg to the dollar and revalued the currency in July 2005. The 0.74 percent monthly gain in May was the biggest since the end of the fixed exchange rate.

China will move at its own pace on the currency, Vice Premier Wu Yi said last month at the close of the talks with Paulson in Washington. The government widened the yuan's trading band on May 18 to allow moves of as much as 0.5 percent each day against the U.S. dollar, although fluctuations had never reached the previous 0.3 percent limit.

``There will be more friction,'' said Enzio von Pfeil, chief executive at Commercial Economics Asia Ltd. in Hong Kong. ``The U.S. will put out some barriers to imports but the Chinese will then just export their products elsewhere.''

Chinese steelmakers such as Wuhan Iron & Steel Co. and Handan Iron & Steel Co. triggered a petition from U.S. manufacturers last week seeking import duties on welded standard pipe because of alleged subsidies and dumping.

Asset Bubbles

Besides trade tensions, China's boom in overseas sales fuels asset bubbles at home by flooding the financial system with cash. The government last month increased a share-trading tax to cool the stock market. It has also increased interest rates and ordered banks to set aside larger reserves to rein in lending and investment and sold bills to soak up cash.

The CSI 300 Index of shares has fallen 5.7 percent from a May 29 peak. The benchmark is still up 93 percent this year after more than doubling in 2006. It gained 2.5 percent today.

Product warnings in the U.S. have provided ammunition for China's trade critics. Regulators this month told consumers not to use toothpaste made in China because it may contain a chemical used in antifreeze.

Frozen ``monkfish'' may be poisonous puffer-fish, an off- road vehicle for children may cause injury or death, and pet- food additives contained an industrial chemical, according to government statements in May and June.

``Chinese manufacturers make shoddy toys that endanger innocent children, export tainted drugs, and sell poisonous foods and personal-care products in the United States and elsewhere,'' Peter Morici, an economics professor at the University of Maryland, said in an e-mail. ``Surely, with its huge trade surplus, Beijing could import western methods of quality control.''

China says it will revamp the system for regulating food and drug safety. The government also describes some U.S. claims about product dangers as unscientific, exaggerated and wrong.

The May trade gap was the country's fourth-highest monthly surplus on record.

To contact the reporter on this story: Nipa Piboontanasawat in Hong Kong at npiboontanas@bloomberg.net

Last Updated: June 11, 2007 17:25 EDT