China's trade surplus will continue to shrink this year despite the fact that the September figure was the lowest since May, economists said.

The surplus reduction will ease pressure from the United States and the European Union on China to appreciate the yuan, they added.

The predicted fall in the surplus is due to China's increased demand for commodities and the rising cost of imports, they said.

The General Administration of Customs announced on Wednesday that China's exports in September grew by 25.1 percent from a year earlier and imports climbed by 24.1 percent, leading to a monthly surplus of $16.88 billion.

The figure is the lowest since May, and well below this year's highest, $28.7 billion in July. Trade surplus in August was $20 billion.

"China's monthly trade surplus will gradually get smaller during the rest of the year, while the economy outperforms most nations and regions worldwide," said Zhu Baoliang, an economist with the State Information Center.

"China's sustained growth will boost imports, but external demand will decrease amid the slow recovery in developed economies."

China has been under intense international pressure over the past few months to allow its currency to rise, due in large part to a trade surplus that peaked in July and has remained above $16 billion since May.

US Treasury Secretary Timothy Geithner on Wednesday criticized China's currency policy and said it had caused global currency market interventions by some economies.

Jean-Claude Juncker, who chairs meetings of the 16-member euro zone's finance ministers, also said recently that the yuan is "more than undervalued".