China says it will suspend preferential tariff treatment for some chemical imports from Taiwan starting next month. The step comes ahead of Taiwan's presidential election scheduled for January 13.

The Chinese government announced on Thursday that the suspension will apply to 12 chemicals produced in Taiwan, including propylene and xylene.

The preferential tariff rates are stipulated under an economic cooperation framework agreement that was signed in 2010 as a step to liberalize trade.

But China's Commerce Ministry said last week that Taiwan's restrictions on imports of farm and other products from China constitute trade barriers. The ministry criticized Taiwan's ruling Democratic Progressive Party, saying it is unilaterally restricting Chinese imports, and indicated it would take a retaliatory measure.

The Chinese government now says Taiwan should take effective steps to remove such trade restrictions.

Observers say that China is applying pressure on the DPP ahead of next month's presidential election. They also say that Beijing has apparently chosen products that are unlikely to have a major impact on either side.

Plastic items made from propylene are found in a wide range of industries, including autos. Xylene is a solvent used in the printing and construction sectors.

China is a major producer of both chemicals. Some say their supply exceeds demand in the country. The value of Chinese imports of the products is said to be small.