CHINA'S export growth picked up unexpectedly in July against a weak global market, raising trade surplus to the highest level so far this year and adding pressure for a stronger yuan.

Exports in July jumped 20.4 percent from a year earlier to US$175.1 billion, up from June's pace of 17.9 percent. Imports expanded 22.9 percent to US$143.6 billion, also stronger than 19.3 percent a month earlier, the General Administration of Customs said today.

The country's trade surplus stood at US$31.5 billion in July, widening further from June's US$22.3 billion, May's US$13 billion and April's 11.4 billion.

But China's trade surplus for the first seven months still contracted 8.7 percent from a year earlier to US$76.2 billion, thanks to increased imports in earlier months.

"It is unexpected that trade surplus had such a sharp increase in July," said Xue Jun, an analyst at the CITIC Securities Co. "A rising surplus will surely trigger renewed demand for yuan's appreciation."

However, Xue reminded that a faster growth in China's exports was a result of more business with emerging markets who are not major campaigners for a stronger yuan like the US and the EU.

In the first seven months, bilateral trade between China and the US expanded 18.5 percent year on year, much slower than China's overall trade growth of 25.1 percent. China's trade with Europe grew 21.1 percent at the same time.