China has decided to extend an investigation into imported potato starch from the European Union for another month to September 30, the Ministry of Commerce said Monday.

Its move came after reports said the EU is considering raising tariffs on cheap Chinese goods in a bid to save its companies.

China said in May in a preliminary ruling that it would levy countervailing duties of up to 11.19 percent on imports of EU potato starch.

Trade disputes between China and EU have shown signs of escalating this year.

In May, the European Commission, the EU's executive arm, ruled against China's copper plate makers by imposing a countervailing duty of 4 percent to 12 percent. Earlier this month, the EU said it will extend anti-dumping duties on Chinese bicycles and bicycle parts for another five years and raised the duties to 48.5 percent. It also levied a five-year penalty duty of up to 69.7 percent on Chinese wall bricks and floor tiles.

European media reports last week said the EU may impose higher tariffs on Chinese goods.

Bai Ming, a ministry researcher, said the action signaled a tougher EU trade stance against China.

"It is obvious protectionism," Bai said. "Chinese exporters may find it increasingly difficult to enter markets in Europe.'' He added that such action would not help troubled companies in Europe.

Since last Wednesday, China has slapped an anti-dumping duty of between 17.6 percent and 28.8 percent on imported photographic paper and paper board imported from the EU, the United States and Japan.

Trade between China and EU rose 21.1 percent to US$318.6 billion in the first seven months, making the EU the country's largest trading partner.