SHANGHAI, June 12 (AP) -- China's trade surplus expanded to US$13 billion (€10.billion) in May, slightly lower than economists had expected, but a 44 percent increase over a year earlier and the largest monthly surplus so far this year.

China's exports last month totaled US$73.11 billion (€57.8 billion), up 25.1 percent from a year earlier, matching expectations, according to customs data released Monday.

Imports for May totaled US$60.11 billion (€47.5 billion), up 21.7 percent from a year earlier.

The US$13 billion trade surplus in May compared with a US$9 billion surplus in May 2005, and a US$10.5 billion (€8.3 billion) surplus in April.

In the January to May period, China's trade surplus was US$46.8 billion (€37 billion), the data showed.

China's trade surplus has been soaring in recent months after hitting a historic high of US$102 billion last year, more than triple the US$32 billion surplus in 2004.

The persistent surpluses have added to tensions over China's currency controls, which its trading partners say keep the value of the yuan artificially low, making the country's exports cheap in overseas markets.