Trade disputes between China and the United States continued to escalate as the US Department of Commerce on Tuesday said it would impose preliminary duties on imports of China-made potassium phosphate salts and coated paper, accusing the Chinese government of giving subsidies to the manufacturers.

Chinese producers of potassium phosphate salts may have to face a countervailing duty of up to 109 percent if they export their products to the US, while domestic makers of coated paper face a tariff between 4 and 13 percent.

The final ruling will be announced in May. Before the announcement, the US Customs and Border Protection will collect a cash deposit or a bond based on the preliminary rates.

US imports of Chinese potassium phosphate salts soared 228 percent by value from 2006 to US$16.4 million in 2008. The value of Chinese coated paper sold in the US was estimated at US$228.7 million in 2008, Xinhua news agency said.

The two cases emerged less than a week after the US decided to levy a tariff of up to 12.97 percent on Chinese seamless steel tubes.

Yao Jian, spokesman for the Ministry of Commerce, blasted the US "protectionism" actions in the earlier case, saying that "this is the US abusing its own trade relief measures."

Potassium phosphate salts are found in industrial cleaning products, fertilizers and food additives. Coated paper is used to print high-end magazines, catalogues and corporate reports.

Sino-US trade rows have worsened since September when the US decided to impose punitive tariffs on Chinese tires. The disputes quickly spread to other industries, including steel pipes, movies, raw materials, electric blankets and wire deckings.

In the first 11 months of last year, 19 countries launched 103 probes against Chinese products, with their value exceeding US$11.6 billion - a record in cases and amount.